Climatology
Younes Nikookhesal; ali akbar rasoli; Davod Mokhtari; Khalil valizadeh kamran
Volume 26, Issue 80 , August 2022, , Pages 327-317
Abstract
IntroductionInvestigating the effect of drought on water resources of countries plain is high important at optimal management of water resources in the agriculture and natural resources part. The phenomenon of climate change, affects the amount of water existence in aquifer by changing amount of precipitation. ...
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IntroductionInvestigating the effect of drought on water resources of countries plain is high important at optimal management of water resources in the agriculture and natural resources part. The phenomenon of climate change, affects the amount of water existence in aquifer by changing amount of precipitation. The occurrence of consecutive climate droughts affects ground water resources. Knowing and awareness of the effect of time between two phenomenon of drought and hydrological drought, can help managers and planners of the water sector. Over the years, the effect of drought on ground water resources less attention has been paid. In order to understand the state of groundwater resources and optimum management, it is necessary to carry out a thorough study of groundwater fluctuations. In this research, Marand plain is the purpose of this study. Marand Plain is poor in rainfall and has a rainfall of 450 mm / year and at least 150 mm / year which varies in the plains and mountainous regions. In this research, we have tried to investigate the effect of atmospheric drops, including rainfall, on ground water level in the Marand watershed.MethodologyThe Marand plain with 45 °, 15 to 50 minutes east longitude and 37 ° 7 'to 38 ° 56' north latitude and with an area of 42.517 square kilometer is one of the vast plains in the northwest of East Azarbaijan province. Which is selected as the study area. In this study, in order to study the trend of ground water level changes in the Marand Plain, the static surface data of 23 piezometric wells was used during the 2000 to 2016. First, a common statistical period was chosen to analyze the data series (2000 to 2016). Then in order to reconstruct the statistical defects, the correlation between stations and piezometric wells and linear regression method was used. The IDW method was used to calculate the average rainfall of the plain. Finally, the standard water level index (SWI) and the SPI index for the studied basin were calculated and analyzed. Discussion The aim of this study was to investigate the effects of climate drought on the fell of groundwater level in the Marand plain using SPI and SWI indices. Meteorological drought conditions in the Marand plain were calculated using the SPI index on a 12-month time scale. The results and drought accuracy of the rain gauge stations in the studied basin showed that during the study period, the first period of drought since 2005 started gradually with decreasing atmospheric precipitation and continued until 2007 and after a period of humidity short-term, again, a short period of drought from 2008 to 2009 has been on the ruling area. The SWI index was used to survey the status of groundwater level. This indicator also showed that in terms of time and place, the drought based on this index corresponded to the drought caused by the SPI index.Conclusion Using the SPI index, the drought trend was studied in the region. The results showed that during the study period (2000-2016) three drought periods from winter 2005 to beginning of 2009, summer of 2011 to the end of 2012 and winter of 2015 to summer of 2016 occurred. Drought affected areas included the east and center of the study area and the west of the region witnessed more atmospheric precipitation. The SWI index was used to survey the status of groundwater level. The index showed that in terms of time and place, the drought based on this index corresponded to the drought caused by the SPI index. Data analysis showed that these two indices with a time interval of one season had a correlation of 1%. This means that the hydrological drought after a season has a direct impact on the surface of the water. In general, we can conclude from the results of this study that the trend of ground water surface changes has been consistent with the drought and weathering changes in the region. Therefore, the fall of the ground water level of Marand plain can be largely influenced by weathered droughts.
Climatology
Ebrahim Ahmadzadeh; Khalil Valizadeh Kamran; Davod Mokhtari; ali akbar rasoli
Abstract
IntroductionRecently, high extreme and frequency distribution of higher sequence of precipitation have been attended more. Through this, because of geographical characteristics of each area, diverse and different thresholds have been presented and utilized for the mentioned precipitation’s characteristics. ...
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IntroductionRecently, high extreme and frequency distribution of higher sequence of precipitation have been attended more. Through this, because of geographical characteristics of each area, diverse and different thresholds have been presented and utilized for the mentioned precipitation’s characteristics. Through the present research, for exploring and analyzing the extreme precipitation event in Tehran through the 1983-2016 statistical periods, some of the indexes presented by World Meteorological Organization Committee were utilized.Data and MethodThe study area in the present study is Tehran province. Tehran province is located in the center of Tehran, with an area of about 12981 square kilometers, between 34 to 36.5 degrees north latitude and 50 to 53 degrees east longitude. Data from Abali and Mehrabad synoptic stations were selected daily for use in the present study during the statistical period of 2016-1983. Before analysis, the data were subjected to quality control and homogeneity test. In cases where for any reason there were incomplete data in the data series of each station, they were reconstructed and supplemented.Analysis of non-parametric I-Kendall trend and age slope estimatorIn the present study, in order to study and analyze the trend of limit events, the indexes provided by the National Climate Committee of the World Meteorological Organization and the Acceptable Research and Climate Prediction Research Program, abbreviated as ETCCDMI, are used. These indexes are part of a set of indexes presented by the World Meteorological Organization's Working Group on Climate Change (Peterson et al., 200: 341), which are used by numerous researchers for analysis in different parts of the world.Model of peak values Above the threshold (POT)The POT first fits the set limit and then one above this threshold with the generalized parity distribution. In the present study, the ninety-fifth percentile was considered as the initial threshold (Coelho et al., 2008: 120; Friederichs, 2010, 211). The test threshold was then set to determine whether it was appropriate or inappropriate. In recent years, two visual methods have been developed to select the threshold. In the present study, methods were used to validate the selected threshold. The first method is the description of residual life, also known as conditional excess (Lechner et al., 1992: 229). In the MRL method, the excess rate is plotted from the threshold to the threshold .How to estimate GDP distribution parameters using the maximum likelihood methodFor different estimates, there are several methods such as torques, possible weighted moments, the existence of correct representation, and so on. However, the most efficient performance method is evaluated as the most complete method (Rao and Hamed, 2000: 21). Therefore, in the present study, the correct method of displaying the work was used.Results and DiscussionThe results of man-condensate precipitation statistics at the studied stations. The results obtained from Mann-Kendall test showed that no significant trend in success level was experienced in the studied stations in the statistical period of 1983-2016. Except that in Abali station, the reduction of the number of consecutive dry days and in Mehrabad station, the reduction of the one-day rate (PX1day) at the level of 90% is significant. One day exhibition at Mehrabad station is a downward trend in the level of 90% confidence with the rate of 1.9 days in the last decade.During the statistical period of 2016-1983, no significant trend was experienced in relation to the index of the number of values for 5 consecutive days. The annual show on other days does not make sense. The number of days with more than 10 mm (R10) and the number of days with more than 20 mm (R20) and the number of days with threshold (Rnn) in the two study stations are not significant.In this study, using the Mann-Kendall non-parameter test and sen slope estimator, the final rainfall trend analysis was performed at Abali and Mehrabad stations. According to the results of the Mann-Kendall test, the display of consecutive dry days (CDD) showed a decrease of 8.5 days per decade at Abali station. But on consecutive wet days (CWD) the upward trends are not significant. The Daily Intensity Index (SDII) is also significant without trend. One day exhibition at Mehrabad station is a downward trend in the level of 90% confidence with the rate of 1.9 days in the last decade. In Abali station with confidence intervals (-0.08, -0.11) and Mehrabad station with confidence intervals (-0.09), the figure is zero. Therefore, in these stations, it has a thin sequence with finite torque that is close to producing a show.The study of growth curves showed that in the 34-year statistical period (1983-2016), most events in stations have a return period of 1 to 10 years. In higher return periods, fewer observations are consistent. The confidence bands of the growth curves also showed to some extent that the deviation of the POT model is less even in the return periods. But as the return period increases, the confidence interval increases. This indicates that as the period increases, the uncertainty in the results increases that the extrapolation of the data is in the range beyond the time frame of the statistical period under study (34 years). Reliable bands have shown that return periods of 1000 years are too unreliable to use in practical applications.ConclusionThe aim of this study is to investigate the changes in the intensity and frequency in Tehran province during the period 1983-1916. In this regard, the study of the initial trend of rainfall showed that in relation to the marginal rainfall, most of the backgrounds had a downward trend in the region. The study of the sequence behavior of events and the frequency and intensity of these events, using them, are higher than the thresholds that have increased in frequency in the study areas. The results of this part of the study are highly consistent with the work of Rahimzadeh et al. (2009) who reported negative trends for cold-bounded appearances and thresholds for precipitation and positive trends for warm-range indices in 27 synoptic stations in Iran. . Rahimzadeh and Hedayat Dezfuli (2011) also showed intensification of heating and decrease along with extreme fluctuations and temperature limit power in Hormozgan province and Mohammadi and Taghavi research (2005) increased the frequency of hot limit indices and cold limit index indices in the city. Has stated Tehran. Maroufi et al. (2011) have achieved similar results in studying the trend of borderline events in the northern and southern coasts of Iran. Also, the estimates and severity of precipitation boundary events using the mean time intervals between events (ARIs) indicate return periods of 1 to 10 years for boundary precipitation. Finally, the resulting Q - Q diagrams and Chi - square test (χ 2) showed that the POT model has great potential for modeling precipitation limit events in the study area.
Climatology
saeid Jahanbakhshasl; Behrouz Sari Sarraf; Hossein asakereh; soheila shirmohamadi
Abstract
Introduction Climate extreme events have expanded and intensified during the 21st century. Extreme precipitation event annually leads to severe damage in agriculture, environment, infrastructures and even the human loss. Therefore, identification of the behavior of such events is one of the pivotal aspects ...
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Introduction Climate extreme events have expanded and intensified during the 21st century. Extreme precipitation event annually leads to severe damage in agriculture, environment, infrastructures and even the human loss. Therefore, identification of the behavior of such events is one of the pivotal aspects of climatic change and the increase of information about extreme precipitation is tangibly necessary for the society especially with regard to those, living in the areas with high risk of flood. extreme precipitation events can be defined as significant deviations from the precipitation mean. As a result, to identify such precipitations, a criterion was needed to evaluate the rate of precipitation values’ deviation from mean. Importantly, given the different types of indicators and thresholds proposed for extracting extreme precipitation, choosing an appropriate threshold with climatology conditions of the study region which could also be capable of identifying extreme precipitation optimally in terms of amount and frequency, requires high precision. The present study aimed at identifying the extreme precipitation events in the west of Iran through introducing the appropriate threshold and spatial scale for the extraction and investigation of these events.Data and MethodsThe west of Iran with the areaof 230760 square kilometers includes about 14% of total area of Iran. Zagros Mountains, stretching from northwest to southeast, are the most important feature of the west of Iran. Two databases have been used in this study. The first database regardsthe precipitation data of 1129 synoptic stations, climatology and rain gauge in the west of Iran. The stations statistics have been checked in terms of existence of any outlier. Ultimately 823 stations out of 1129, were used for producing gridded data. The gridded data, are the results from the interpolation of daily precipitation observations since January 1st 1965 to December 31st 2016, using Kriging interpolation method and spatial separation of 6*6 kilometers. the final base, a matrix possessing the dimensions of18993*6410 (representing time on the rows and place on the columns) was developed. The second database referred to the Sea-level pressure patterns (Hectopascal).To identify such precipitations, in addition to the main threshold that includesthe mean of precipitation more than 75th percentile for each pixel per day of a year, a second threshold including the standard deviation of these precipitations (with the values of one, two, and three times more) has been also added to the mean. Accordingly, three groups of extreme precipitation were identified in the region which were separated according to the spatial zone that had been covered. Moreover, the sea-level pressure patterns were extracted with regard to these precipitations for each zone andthen classified using clustering analysis technique.Results and Discussionthree groups of precipitations with different coverage zoneswere identified: 1- 83 days with equal to or more precipitation than the mean of precipitations more than 75th percentile plus one time standard deviation which cover more than 40% of the region. 2- 144 days with equal to or more precipitation than the mean of precipitations more than 75th percentile plus two times standard deviation which cover more than 20% of the region. 3- 82 days with equal to or more precipitation than the mean of precipitations more than 75th percentile plus three times standard deviation which cover more than 20%The maps of 7 participation groups of the first type in comparison with 6 precipitation groups of the second and third type contain common and repetitive patterns. Each precipitation maps of the second and third types explains a type of patternand there is minimum overlapping in the maps. Therefore, the precipitations are obtained from the most particular and distinct atmospheric patterns. considering the three properties of 1- equality of precipitation groups of type two and three (both include 6 groups of atmospheric patterns). 2- repeating the atmospheric patterns of precipitation of type two prominently in the precipitations of type three. 3- the formation of the most optimum atmospheric modeling for the precipitations of both thresholds in the zones of 20% and higher, in the west of Iran, the extreme precipitations refer to those with higher means of recipitations more than 75th percentile plus two times standard deviations,have mostly occurred in the zone of 20% and higher of the region.
Climatology
Soodabheh Namdari; Ali Hajibaglou; GholamReza Abazari
Abstract
IntroductionAtmospheric mineral dust particles play a key role in the radiation budget of the atmosphere and the hydrological cycle, and have an important effect on public health by disrupting climate systems and air pollution. Due to Iran’s location in the arid and semi-arid belt of the world, ...
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IntroductionAtmospheric mineral dust particles play a key role in the radiation budget of the atmosphere and the hydrological cycle, and have an important effect on public health by disrupting climate systems and air pollution. Due to Iran’s location in the arid and semi-arid belt of the world, Iran is constantly exposed to local and regional dust systems. Considering the importance of the negative effects of dust storms and their increasing trend in some dust sources, the study of these changes in the last two decades show the importance of the dust storms in recent years. Moreover, spatial-temporal identification and analysis of the properties of these dust particles is very important in order to manage this crisis and prevent the harmful effects of dust particles. In Iran, due to desert conditions, the presence of dust hotspots has always caused air pollution and reduced the quality of life of people. In recent years, some dust hotspots have been ambiguous about increasing the intensity of dust emission. In this study, using the AOD product of MODIS, which compute the dust intensity, and based on the annual frequency and averages of dusty days, the location of dust hotspots were identified and then the trend of dust intensity in each hotspots were examine. The results showed that despite the relatively similar climate, the trend of changes in these dust hotspots does not follow the same pattern and complex human activities and natural changes.Data and Method In this study AOD product from MODIS with the resolution of 10 km was used to extract dust information then the frequencies of days with AOD greater than 0.6 per year were extracted. In addition to correctly calculating the average of AODs, calculating the number of days without data is also important in the results. The spatial and temporal distribution of the study period, were identified in three periods, 2000-2006, 2007-2012 and 2013-2018. The percentage of changes in each of the dust sources compared in different periods. The standard deviation was extracted to identify the areas most vulnerable to dust storms. Finally, to detect the quantitative distribution, the trend of AOD changes in the extracted dust hotspots was used to investigate the changes in the dust intensity trends.Results and DiscussionThe map of dust hotspots in the first period shows the main dust sources are in the north of Sistan and Baluchestan (Zabol) and south of Sistan and Baluchestan (Chahbahar), in the southeast of Semnan (Dasht Kavir), Damghan, Garmsar, Jazmourian, southwest of Hormozgan, (Bandar Lengeh area), south and southwest of Khuzestan, southwest of Yazd (Nayer), as well as parts of Qom, Ilam (Mehran), Isfahan, and south of Fars provinces. In the second period of study, many dust centers have become more intense and extensive. According to the map of dust centers in the third period of studies, compared to the first and second periods, the area of dust centers has decreased.According to the results, about half of the areas without emission has been turned into areas with dust with different frequencies in second period, and also about half of the area of very high-frequency hotspots has been turned into other dust sources with less intensity in the third period. Also, the most fluctuations in dust intensity have occurred in Sistan, Jazmorian, southeast of Semnan, East Azerbaijan, Zanjan and Khuzestan provinces. The results of trend analysis of dust intensity in different dust hotspots show that despite the relatively uniform climate, the dust sources trends in different dust sources do not follow the same pattern.ConclusionDue to the geographical location of Iran and the existence of vast deserts, the wethear has always affected by dust sources of inside and outside of the country. In this study, using satellite data with appropriate resolution, the location of dust sources in three time periods were extracted. The changes of each dust intensity class in the second and third periods were compared with the first period so that regardless of location, changes in dust intensity can be evaluated in general. Then, using the standard deviation method, the dust hotspots with the highest percentage of changes were identified. Finally, the trend of changes was calculated by examining the trends of changes in 24 main dust centers. According to the results of the present study, many changes have been observed in some dust sources and the intensity of dust in many dust sources has decreased. While some sources such as Isfahan, and Khuzestan province due to the role of human factors such as agricultural activities as well as the reduction of surface and ground water and as a result of drought and changes in soil texture have an increasing in trend of dust intensity. Since a decreasing trend is observed in most of dust sources, eastern and southern parts of Iran, the results of this study indicate the key role of climatic factors in changes and fluctuations in dust emission in Iran. Because climatic factor can be the only factor which has a relatively uniform effect on the dust emission on a large scale of Iran.
Climatology
Naser Jafarbegloo; Ali Mohammad khorshiddoust; majid rezaei banafsheh; Hashem Rostamzadeh
Abstract
INTRODUCTION
Today, pre-risk awareness has become an integral part of the national development management and planning system in many countries (Civiacumar et al., 2005). Agriculture is inherently sensitive to climatic conditions. The minimum temperature, which has been identified as the most vital ...
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INTRODUCTION
Today, pre-risk awareness has become an integral part of the national development management and planning system in many countries (Civiacumar et al., 2005). Agriculture is inherently sensitive to climatic conditions. The minimum temperature, which has been identified as the most vital determining factor in the distribution of plant species on the planet, can be both a limiting factor and a factor in the spread and species distribution (Rodrigo, 2000: 155). Therefore, in this study, we examined the changes in minimum temperatures in the statistical period (1980-2010) and predicted these changes in the 2050s (2065-2046) in the Northwest of the country using the LARS-WG microscale method and model output. Atmospheric pairings of HadCM3 and MPEH5 were addressed. The prediction of minimum temperature variations to determine the extent of its future changes and considering the necessary measures to minimize the adverse effects of climate change on agricultural products were of great importance. In this regard, general atmospheric circulation models (GCMs) are designed that can simulate climatic parameters.
DATA AND METHODS
In the present study, the output data of two HadCM3 and MPEH5 general circulation models based on two scenarios A2 and B1 were analyzed by LARS-WG statistical method in 21 synoptic stations located in the Northwest of the country. The results were monthly and periodic on the base period (1980-1999) and the 2050s (2046-2065), thereby the minimum temperature was evaluated and analyzed. In assessing the LARS-WG model, the observational and simulation error data were evaluated using MSE, RMSE, MAE and R2, and the model was evaluated for the appropriate region. The results showed that the minimum temperature in the future period will increase compared to the base period in the study area. This increase in air temperature at the study area is based on the HadCM3 and MPEH5 models, on average, 1.9 and 1.7 degrees Celsius to 2065 horizons compared to the base period. The north-eastern part of the northwestern region of Iran will have higher temperatures than the semi-southern regions. In fact, the cooler regions of the high latitudes will face more incremental changes in the amount of minimum temperatures. The results and achievements of this research are important for long-term plans for adaptive measures in the management of fruit gardens, agricultural products and water resources management. In order to calibrate and ensure the accuracy of the LARS-WG microscale model, the model was first implemented for the basic statistical period (1980-2010); then the minimum temperature output and its standard deviation were compared with the observational data of the studied stations, which indicated a small difference between the observed and simulated values and also deviated from their criteria.
RESULTS AND DISCUSSION
The results of evaluation of observational and simulated data by LARS-WG microscale model using RMSE, MSE and MAE error measurement indices for the studied stations indicate that there is a significant difference between the simulated values and the values of the observed observations. There is no critical 0.05 significance levels, and Pearson correlation values between simulated and real data are acceptable at the significance level of 0.01. The obtained results show that the accuracy of the model varies in different stations. In general, the results of error measurement indices indicate that the LARS-WG model is of good accuracy for micro-scaling the parameters under study. In order to better represent and ensure the accuracy of the prediction as well as to investigate the uncertainties in the studied models, the simulated values were compared and observations were made on a long-term average during the base period in the studied stations using comparative graphs. As can be seen, the observed and generated values in the base period at all stations are very close to each other and the LARS-WG model has been successful in simulating the studied parameter. After evaluating the LARS-WG model and ensuring its suitability, the data predicted by the model for two scenarios A2 and B1 using HadCM3 and MPEH5 models and were examined on a monthly and long-term basis. The study of the status of minimum temperature changes of the studied stations in the future period (2065-2056) shows that the minimum temperature is based on both scenarios and in all months and stations compared to the period, the base has increased. Due to the large number of study stations, only stations located in provincial centers of this study are listed.
CONCLUSION
Cold and frost are one of the most significant climatic hazards on fruit trees. This type of climate risk affects different parts every year, especially the cold regions of the northwest of the country. Studies show that in recent years, the rate of economic damage to fruit trees in this region has increased, so in this study, the outlook for changes in minimum temperatures in this region using the LARS-WG statistical microscale model and output two HadCM3 global model and MPEH5 were introduced in the 2050s (2065-2046). For accuracy and precision of the models, error measurement indices and coefficients of determination and correlation were used. The results showed that the LARS-WG model has a good ability to simulate the studied variables in the study area. The results of long-term prediction of the studied models show that the minimum temperature values will increase in all study stations, which is based on HadCM3 and MPEH5 models on average. In the 2050s, and it will be 1.9 and 1.7 respectively, compared to the base period. The results of the studies of Kayo et al. (2016), Sharma et al. (2017), Khalil Aghdam et al. (2012), Qaderzadeh (2015), Sobhani et al. (2015) and Khalili et al. (2015) were confirmed. In general, based on the studied scenarios and models, the minimum temperatures are expected to increase in the study area in the future. By increasing it, the yield of some crops that need cold during the growing and productive period would decrease. It can also reduce snowfall, followed by frost on crops and lack of water in dry seasons. Therefore, due to the fact that following the climate changes, the conditions of the agricultural climatology are also changing, it is necessary for the relevant officials and planners in the agricultural sectors to adopt the necessary strategies to reduce the consequences and adapt to the new climate.
Climatology
Parichehr mesri alamdari; seyed Hassan rasouli
Abstract
Introduction
With the beginning of the Industrial Revolution in 1830 and the growing growth of human knowledge, various changes have taken place in human life and human needs for energy and consumption of fossil fuels such as coal, oil and natural gas have led to a sharp increase in materials such as ...
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Introduction
With the beginning of the Industrial Revolution in 1830 and the growing growth of human knowledge, various changes have taken place in human life and human needs for energy and consumption of fossil fuels such as coal, oil and natural gas have led to a sharp increase in materials such as Carbon dioxide has been released into the atmosphere. Increasing its population exacerbates this phenomenon. All of these changes have caused the weather to change. The phenomenon of climate change, which is mainly related to the increase of greenhouse gases in the atmosphere, is a clear example in this field. This phenomenon causes many current problems such as gradual warming of the climate, melting of ice, rising sea levels, torrential rains, increasing drought, acid rain and threats to human health. And wildlife species in different regions of the earth (Atabi et al., 2007: 146). The development of urbanization and migration of rural residents to cities to enjoy the benefits of civilization, especially in the second half of the twentieth century led to the overdevelopment of cities (Alijani et al., 2010: 541). The desirability and quality of urban areas make a difference in the value of land use. Knowledge of how urban temperature patterns are distributed allows planners to manage the construction of urban green space to adjust the temperature. Also, by studying the relationship between user patterns and the distribution of thermal patterns, it is possible to provide programs to change and relocate these uses to improve environmental conditions. Despite the year-on-year changes in the average temperature due to the natural variability of the climate, increasing trends in the average annual temperature are evident in most parts of Iran, including the city of Sari. These increasing trends are mainly due to the increase of greenhouse gases in the atmosphere (due to the burning of fossil fuels and changes in the surface characteristics of urban areas (Alizadeh Chobari et al., 2016: 571 and 572). In this regard, the city Sari is located in a dense area of activity and residential centers and with its various capabilities has been able to enjoy a special position in the province.This city due to its strategic location and suitable climate and location Tourism and unique agricultural capabilities are facing population growth and increased migration. Considering the challenges such as the increasing growth of the urban population, the uneven expansion of cities, the destruction of the environment, etc., which has reduced the quality of life and created heterogeneous uses in different urban areas; As a result, the climatic parameters of the region are also subject to change. In this regard, the effect of these changes on the city of Sari and solutions to deal with it have been studied.
Methodology
The present research is applied-developmental for the purpose and is descriptive-analytical according to the method of work. In this study, in order to measure the spatial distribution of population in the eleven districts of Sari, data under the Geographic Information System (GIS) has been used. In order to investigate the spatial distribution of population in each area of Sari, the Shannon relative entropy model has been used and to calculate the maximum thermal island intensity, the Oke numerical-theoretical equation has been used. Sari, the capital of Mazandaran province in northern Iran, is one of the largest and most populous cities in Mazandaran province and the north of the country, which is located at 53 degrees and 37 minutes east longitude and 34 degrees and 36 minutes north latitude. In terms of natural location, this city is located in the south of the Caspian Sea and in the plains of Sari city and only its southern and southwestern parts lead to mountains and low satellite hills. The height of the city from the sea level is 18.5 meters and the difference in its area to the coast of the Caspian Sea is 24 kilometers. The general slope of the city is from south to north and is very gentle (Sari Master Plan Studies, Mazand Tarh Consulting Engineers, 2015).
Results and Discussion
In the present study, the relationship between the spatial distribution of the population and the creation of thermal islands in the city of Sari has been investigated. After examining the spatial distribution of population and the intensity of changes in thermal islands, it is concluded that there is a relative relationship between the two indicators of spatial distribution of population and the intensity of changes in thermal islands in Sari. In region 2 of region 3 of Sari city, which had the lowest equilibrium in the spatial distribution of population, the intensity of changes in thermal islands was also low, and in areas where the spatial distribution of population was semi-balanced (region one of region one, regions 1 and 2 from region 2, and region 1 from region 3 of Sari city), the intensity of thermal island changes was low. Also, in the areas where the spatial distribution of the population was balanced (areas 2, 3 and 4 of area one, areas 3 and 4 of area 2 and area one of area 4), the intensity of thermal island changes was low and moderate.
The results indicate the fact that there is a direct relationship between net residential density and the intensity of changes in thermal islands in the city of Sari. As the net residential density increases, the intensity of changes in thermal islands in Sari city increases, and as the net residential density decreases, the intensity of thermal island changes decreases. Based on the findings of the survey of Sari city areas and analysis of the spatial distribution of population and the maximum intensity of thermal island changes, it is concluded that there is a relative relationship between these two indicators in Sari city areas. In the areas that had the lowest equilibrium in the spatial distribution of the population, more intensity changes were observed in the thermal islands and in the areas where the spatial distribution of the population was semi-balanced and balanced, the intensity of changes was less in the heat islands. On the other hand, according to the results of Spearman correlation coefficient, it can be said that the most important effective factor in the maximum intensity of thermal island changes, which is inversely related to this phenomenon, is the net residential density. Areas in Sari that have the highest intensity of thermal island changes
They also had the lowest net residential density. Therefore, it is necessary to apply appropriate policies such as revising and improving management in the way of population loading in various urban development plans and planning for the management and organization of urban structures in relation to the intensity of changes in thermal islands. Can be effective. It can also provide favorable grounds for guiding the development of population policies in various urban development plans to create a balance with sustainability in the city of Sari.
Climatology
Seyed Hossein Mirmousavi; Zahara Taran
Abstract
Introduction
Dust is one of the most common climatic phenomena in arid and semi-arid regions of the world The phenomenon of dust is a natural occurrence and occurs in areas with vast areas of arid and desert areas, Lack vegetation and other surface coatings. Due to its presence in the arid and semi-arid ...
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Introduction
Dust is one of the most common climatic phenomena in arid and semi-arid regions of the world The phenomenon of dust is a natural occurrence and occurs in areas with vast areas of arid and desert areas, Lack vegetation and other surface coatings. Due to its presence in the arid and semi-arid belt of the world, Iran is constantly exposed to local and synoptic dust and dust systems. In recent years, the phenomenon of dust in the Middle East has been increasing, Because it is one of the five regions of the world that has the highest dust production . Long periods of drought and inappropriate interventions in nature can increase the likelihood of this phenomenon.
In recent years, the trend of dust events in the west and south of Iran, especially in the spring and summer, has increased dramatically .This phenomenon is affected by certain atmospheric conditions and its distribution can affect the temperature, temperature, precipitation and atmospheric circulation conditions of the area during the months of the year.
Materials and methods
In this study, data of 56 years old (during 1961-2016) precipitation, temperature and dust on daily scale from 30 synoptic stations in the west and southwest of Iran were obtained from the country's meteorological organization. In line with this study, MATLAB, ArcGIS and SURFER softwares have been used. In order to analyze the information, recognition of fluctuations and the relationship between dust, temperature and precipitation have been used.
Results and discussion
Recognition of fluctuations and the relationship between dust, temperature and precipitation are investigated using regression, spectral analysis and Pearson correlation coefficient. Then it is represented by trend maps, cycles, and correlation tables. The results for the West and Southwest of Iran have been obtained and explained in detail.
Conclusion
The study of the spatial distribution of the trend shows that most of the stations studied in the dust and rainfall have an increasing trend and have been in a decreasing trend temperature. Spectral analysis of dust, dry days, and temperature showed that short-cycle cycles in addition to the most frequent distribution, showed a higher probability of occurrence than long-term periods. In most of the stations studied, the correlation of dust with temperature and dry days has a positive and direct, relationship with the rainfall has a negative and inverse relationship. The local mororan analysis for the spatial autocorrelation of dust with dry days in the western, northwest, northern and parts of the east of the study area has shown a high value cluster pattern (positive spatial autocorrelation). The spatial autocorrelation of dust with precipitation in the northeastern, eastern, and small parts of the southeast and west of the study area has a high cluster pattern (positive spatial autocorrelation). The spatial autocorrelation of dust with temperature in the eastern, western, and small parts of the south of the range has a high cluster pattern (positive spatial autocorrelation).
Climatology
mehdi asadi; Ali mohammad khorshiddoust; Hassan Haji Mohamadi
Abstract
Introduction
Data and information from the Meteorological Department of India and the Joint Hurricane Warning Center (JHWC) were used to investigate the structural nature of Ashuba tropical storm in the Arabian Sea from June 7 to June 12, 2015. To study the atmospheric structure, the analyzed digital ...
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Introduction
Data and information from the Meteorological Department of India and the Joint Hurricane Warning Center (JHWC) were used to investigate the structural nature of Ashuba tropical storm in the Arabian Sea from June 7 to June 12, 2015. To study the atmospheric structure, the analyzed digital data were taken from the European Center for Medium-Term Forecasts and the Center for Environmental/Atmospheric Forecasts (NCEP/NCAR) for the Arabian Sea and beyond. The study area was the Arabian Sea, located between the Indian subcontinent (eastern part) and the Arabian Peninsula (western part) and northwest of the Indian Ocean. On average, 1-2 tropical cyclones form on the Arabian Sea each year. Even in some tropical regions, strong cyclonic cycles occur at the synoptic scale (Evan & Camargo, 2001: 145). Therefore, from previous years, climatologists have studied the types of storms, due to the increase in tropical cyclones in the last decade; and thereby, this issue is followed with more sensitivity. Consequently, the main purpose of this study was to explore the structural nature of Ashuba tropical storm on the Arabian Sea in order to identify one of the region's main moisture sources.
Materials and Methods
Storm data statistics were obtained from the Meteorological Department of India and the Hawaii Hurricane Warning Center. Analyzed digital data, including; Geopotential altitude (Hgt), orbital (u), meridional wind (v), sea surface pressure (SLP), air temperature and sea water temperature (SST) for standard levels at 17 compression levels with a resolution of average daily geographic degree belonged to the National Center for Environmental Prediction/Atmospheric Science and precipitated networked data were obtained from the European Center for Medium-Term Atmospheric Forecasting (ECMWF) with a resolution of 0.125 degrees Celsius for the Arabian Sea. NASA and MODIS satellite imagery were also used for the visible band for every six days. The CAPE index was applied to evaluate the energy required by the storm supplier.
Findings and Discussion
The results of study displayed that in the middle level of the atmosphere, while forming a low-altitude nucleus with very strong positive rotation, the conditions for the production of tropical storms in the region have been provided. On the other hand, on the surface, low pressure has formed in the southeast of the Arabian Sea with a central pressure of 995 hPa and has started moving westwards towards the coasts of Oman and northern Yemen. Creating a very strong convergence current on the surface and upper divergence caused the storm to reach its maximum strength in the region on June 9. However, the anomalous temperature of the water surface in the range where the storm reached its maximum intensity reaches to over than 5 degrees Celsius. The increase in water surface temperature and the transfer of heat and moisture into the storm has strengthened and, by its nature, caused heavy rainfall in the region. Finally, on June 12, as it approached the east coast of Oman, it began to disappear due to lack of moisture for its dynamic movements, and changed from a tropical storm to a tropical hurricane. Also examining the prepared maps for the amount of precipitation and the flow of the lower levels of the atmosphere, it was determined that on the first day of the storm, a cyclonic current occurred in the east of the Arabian Sea, resulting in the maximum amount of precipitation in the west of the system, which reaches more than 240 mm. On the second day, moving north of the system, the amount of precipitation was concentrated in the south, so that the southern coast of India was not unaffected by precipitation and had about 120 mm of rainfall. On the third day, with the placement of this tropical storm in the north of the Arabian Sea, the maximum precipitation was created in the east of the system, which was more than 160 mm. On the fourth day, the western half of the Indian coast was faced with a rainfall of nearly 110 mm, which was due to its location in the east of the cyclone, which in turn caused the rise of air and the transfer of moisture to the air parcel, floods in the region. On the fifth day, the maximum rainfall was close to the eye of the storm, which was close to 100 mm, and the coastal areas of the Indian subcontinent were still experiencing heavy rainfall. Examination of the 850 hPa pressure system revealed that on the first day, the maximum relative pressure system nucleus formed in the southeastern parts of the Arabian Sea. These conditions have led to very strong convergence in the lower levels. The presence of such strong convergence and amplification of rotation has caused this anomaly to reach its maximum in the region. The strong rotating nucleus then extended to the west coast of India and then moved westward on the third day to the central regions of the Arabian Sea, with a very strong rotating current extending from latitudes 10 to 30 degrees north. As the storm/hurricane approached the west coast of the Arabian Sea, it intensified to more than five pressure system units on the fourth day. On the fifth day, the positive nucleus became independent and formed a very strong rotating closed cell. On the sixth day, with the cyclone remaining on the eastern coast of the Arabian Peninsula, its power had gradually diminished.
Considering the water temperature in the region, which is an average of 6 days, it showed that the water temperature in most parts of the Arabian Sea was high, so that these conditions reached more than 32 degrees Celsius in the coasts of India and the center of the Arabian Sea. These conditions were less only in the northern regions of the sea than in other regions. To understand the water surface temperature, its anomaly was also calculated for six days with the storm. Its output indicated that the eastern, northern, western and southwestern regions of the Arabian Sea were associated with a positive anomaly of 2 to 3° C. Negative anomalies only reached -1.5 degrees Celsius in the north and south of the sea. Occurrence of maximum positive anomalies in the region was one of the main reasons for the intensification of cyclones in the region, so that the western regions of the Arabian Sea had the maximum positive anomalies and on the other hand the maximum area of tropical cyclone activity.
The 12-hour reports from the Indian Meteorological Agency and the Hawaii Hurricane Warning Center were used to route the tropical storm. In these two centers, there were several data methods for routing and the origin of the storm. Geographical coordinate data with a 12-hour separation was used, which from the beginning of the storm to its decline, its characteristics and longitude and latitude were recorded as a text file. The onset of the storm was from the eastern part of the Arabian Sea, which migrated northward to higher elevations and deviated in its path due to the dominance of the Coriolis to the west of the region and disappeared off the coast of Oman.
Conclusion
Ashuba tropical storm/hurricane formed on June 7, 2015 in the Arabian Sea and disappeared on June 12, 2015. This investigation revealed that on the first day, a low-lying cell was formed in the eastern part of the Arabian Sea, during which a positive rotating nucleus or vortex was formed in the mentioned area and strengthened in the following days. The role of the Arabian Sea and abnormal changes in its water surface temperature in the occurrence of hurricanes has been mentioned in the researches of Ghavidel Rahimi (2015: 31) and Lashkari and Kaykhosravi (2010: 19). On June 9, as the subtropical anticyclone expanded further east, the Arabian Sea's low-pressure cell became oval in a circle, contributing to the deepening of the system, creating another bond at the heart of the closed cell with a height of 5,810 geopotential meters. In the last days, as the coasts of Oman and Yemen approach, the intensity of this cell decreases and its extinction stage was reached. On the surface, in parallel with the mentioned period, a low-pressure core with a central pressure of 995 hPa formed on the southeast of the Arabian Sea and the creation of a very strong positive rotation indicates the occurrence of hurricanes in the region. The central pressure of the storm reached less than 993 hPa on days 9 and 10, which was the peak of the storm. As it approached the shores, the intensity of this cyclone was greatly reduced, turning it from a tropical storm into a tropical turbulence. Examination of the water surface temperature showed that the average water surface temperature in these 6 days in most parts of the Arabian Sea was more than 29 degrees Celsius. Inspection of water surface temperature anomalies also disclosed that the maximum positive anomalies corresponded to several places in the sea, including the southern coasts of Pakistan to western India, eastern Oman and a very strong core corresponding to the southwest of the Arabian Sea with an average temperature of more than 5° C. The maximum rainfall inside the cyclone indicated that on the first day of the storm, the maximum rainfall in the southwest was 240 mm. In the following days, with the transfer of this core to the south, southeast and finally to the east, the maximum rainfall would be on the west side of the Indian coast. Only in the last days it was observed that while the maximum rainfall occured in India near the eastern part of the eye of the storm, a maximum precipitation center with an average of 100 mm has been created. In this study, two indicators, CAPE and SWEAT, were used to assess the location of storm formation. The results showed that these two indicators well showed the formation and severity and weakness of the storm during different stages. Thus, on the first day in the south of the Arabian Sea, the amount of CAPE was more than 5000 Jules/kg, which indicates the amount of convective energy available. On the other hand, the values of the SWEAT index have reached more than 380, which specify that the probability of a hurricane in this region is very high. Also, with the increase of water surface temperature in the region and the increase of anomalies in it, the necessary energy is provided for the production of cyclones in the region, which with the increase of energy within the air mass system and the presence of buoyancy energy in it, and on the other hand, instability indicators in monitoring and tracking these types of storms showed that they are a suitable tool for tracking and are able to navigate it while being aware of the intensity of the storm.
Climatology
Zeynab Jawanshir; Khalil Valizadeh Kamran; Aliakbar Rasouly; Hashem Rostamzadeh
Abstract
Introduction
For the first time, Faddingham presented a geographic weight regression model. He tried to study the aspects of space heterogeneity. After that, Bronson examined the relationship between housing prices and areas. Which encountered a number of issues in relation to the model, which included ...
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Introduction
For the first time, Faddingham presented a geographic weight regression model. He tried to study the aspects of space heterogeneity. After that, Bronson examined the relationship between housing prices and areas. Which encountered a number of issues in relation to the model, which included the selection of variables, bandwidth and spatial correlation errors. Using the GWR, Franklin analyzed the spatial characteristics of the rainfall along with the elevation changes. Elvi also used this model to study the spatial factors that affect land prices. The GWR produces spatial information that expresses spatial variations between variables' relationships. Therefore, the maps produced from these analyzes play a key role in the spatial non-static description and interpretation of variables (Mennis 2006) and an equation Generates a separate regression for each observation instead of calibrating an equation, so it allows the parameter values to be continuously changed in the geographic space. Each of the equations is calibrated using a different weight of the observations contained in the total data. And more relative weights are assigned to closer observations and less or zero weights to those who are far away.
Data and Method
The Surface Energy Balance Algorithm for Land (SEBAL) calculates the surface heat flux instantaneously as well as 24-hour. The latent heat flux shows the energy required for true evapotranspiration and is calculated as the remainder of the equilibrium energy equation (Mobasheri, 2005). In remote sensing estimates of surface Albedo, surface temperature and surface leakage in the thermal infrared region, reflectance is used to calculate spatial variations in short-wave radiation and long-wave radiation emitted from the surface of the earth. A combination of short-wave and long-wave radiation combines the ability to calculate the pure absorbed surface radiation for each image pixel. Each of the equations is calibrated using a different weight of the observations contained in the total data. And more relative weights are assigned to closer observations and less or zero weights to those who are far away. In other words, the GWR only uses geographically close observations to estimate local coefficients. This method of weighting is based on the idea that the use of geographically close observations is the best way to estimate local coefficients. The GWR method not only does not consider the effects of self-variables on the independent variable, but also the effects of neighboring situations. The values of the geographic weighting model can be used to describe the spatial correlation of the factors used. Therefore, we extend the study area to several sections We divide the values of the geographic weight coefficients in each of the sections in relation to each of the environmental parameters. Unlike regular regression models, they provide an equation for describing general relationships between variables. GWR allows the parameter values to be changed continuously in the geographic space. Each of the equations is obtained using a different weight of the observations contained in the total data.
Results and Discussion
The analysis of the relationships between selected indices by geographic weighted regression model and the classification of output values through the normalization of data in seven categories. The values obtained vary between 1 and 1, and the smaller the index, the spatial disjunction is variable, and the larger it shows the presence of spatial clusters. It was found that all three indexes of evapotranspiration, surface temperature and vegetation index have cluster spatial pattern. Therefore, the null hypothesis is based on the spatial correlation itself, and as a result, three of the above indicators can be used for spatial analysis of the actual evaporation. Based on the correlation between the factors affecting the macroeconomic factors, the factor of vegetation index has the most effect on the magnitude of the spatial distribution in the studied area (53% with an area of 471782864 square meters). However, as the results are clear, this number is an overall number and covers the overall situation in the area. And does not refer to spatial features of the area. In the results of weighted regression, the effect of elements can be observed spatially. Accordingly, according to the geographic weighted regression method, the relationship between evapotranspiration and surface temperature was negatively affected and negatively affected. The relationship between dehiscence and vegetation index was studied in different years. The highest digit on the seventh floor is 13/99 and in the area of 266611500, which shows a high positive effect. The relationship between evapotranspiration and the Albedo shows the highest value in the first and second classes. The values of 18 and 10 in the area of 490428000 and 1170753300 m 2, respectively, show a very negative impact and a significant negative effect.
Conclusion
Geographic weighted regression method is a statistical method that is adapted to study local patterns. This method is, in fact, a technical technique that analyzes the relationship between spatial variables in a hypothetical unpopular space. In this research, we tried to express the effect of several indicators on actual evaporation. These indicators are not all indicators that have had an impact on actual evapotranspiration Because actual evapotranspiration is closely related to other climatic factors. Because of the unique ability of spatial weighted regression to identify and analyze the relationships between variables, it is recommended to use it in quantitative analyzes. The Z classes resulting from the GWR analysis of the actual evapotranspiration in different years have different states that indicate the spatial effect of the surface temperature in different conditions.
Climatology
Mohammad Hossein Aalinejad; Saeed jahanbakhsh; Ali Mohammad Khorshiddoust
Abstract
Introduction
Determining the temporal change of snowmelt or agriculture water equivalent of snow, predicting flood, and managing the reservoirs of a region is of utmost importance. Some major parts of the western sections of the country are located in the mountainous region and most of the precipitations ...
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Introduction
Determining the temporal change of snowmelt or agriculture water equivalent of snow, predicting flood, and managing the reservoirs of a region is of utmost importance. Some major parts of the western sections of the country are located in the mountainous region and most of the precipitations of this region occur in the form of snow in winter. The runoff resulting from snowmelt has an important role in feeding the rivers of this region and it has a significant share in developing agriculture and the economy.
Scientific studies have shown that climate change phenomena have significant effects on precipitations, evaporation, perspiration, runoff, and finally water supply. As the demand increases, climate changes, greatness, frequency, and the damage resulting from extreme weather events, as well as the costs of having access to water increase, as well. Therefore, evaluating the runoff resulting from snowmelt and the effect of climate change seems necessary for managing water resources.
Methodology
Gamasiab basin is located in the northeast part of the Karkheh basin originating from the springs in the vicinity of Nahavand. Its basin has an area almost equal to 11040 square kilometers that have been located in the east part having 47 degrees and 7 minutes to 49 degrees and 10 minutes geographical longitude and from the north part, it has 33 degrees and 48 minutes to 34 degrees and 54 minutes geographical latitude. This basin has an altitude between 1275 to 3680 meters.
In this study, snow-related data required for simulation were derived from the daily images of the MODIS sensor. To this end, first, the snow-covered area of the Gamasiab basin was measured during the 2016-2017 water years using the process of satellite images obtained from the MODIS sensor in the google earth engine system. All geometric justifications and calibration processes of images were applied precisely in the mentioned system. In the next step, the output of the GCM model scenarios was utilized for calculating temperature and precipitation changes in future periods. These CMIP5 kind models were under the control of two RCP45 and RCP85 scenarios and were downscaled with LARS-WG statistical model.
Moreover, to investigate the uncertainty of models and scenarios, the best models and scenarios were selected for producing temperature and precipitation data of future periods; accordingly, the outputs of the models for future periods (2021-2040) having the basis period of (1980-2010) were compared using statistical indexes of coefficient of determination (R2) and Root Mean Square Error (RMSE). The results were entered into the SRM model as the inputs. In addition, temperature and precipitation data of meteorological station of the studied region as well as the daily discharge of the river flow of hydrometric station of Chehr Bridge (as located in the output part of Gamasiab basin) were used during the statistical period of October 2016 to May 2018.
Discussion
Using Digital Elevation Model (DEM) of the region and the appendage of Hec-GeoHMS in GIS software, firstly, flow direction map, flow accumulation map, and stream maps were drawn and the output point (hydrometric station of Chehr Bridge) was introduced to the border program of the identified basin and the basin was classified based on the three elevation regions.
Producing temperature and precipitation data of future periods requires a long-term statistical period; accordingly, the meteorological station of Kermanshahd was selected since it was in the vicinity of the studied region. To be confident in the ability of the model in producing data in future periods, the calculated data had to be compared with the observed model and data in the studied stations. The capabilities of the LARS-WG model in modeling the mentioned parameters of this station confirmed the observed data. Moreover, the ability of the model in modeling precipitation was very good and acceptable; however, the most modeling error was related to the precipitation in Mars.
In the next phase and compared to the basic periods, the mean of changes in average precipitation and temperature was measured in the studied stations during January and Juan of 2015 to 2017(for which simulation had occurred); as an index of changing the climate, this was entered into the SRM model under climate change conditions. During the simulation period (January to Juan), it had been predicted that the precipitation parameter would decrease and the temperature parameter would increase.
Conclusion
The results of this study indicated that using the MODIS sensor could provide an acceptable estimation of the snow cover level of the Gamasiab basin, which lacked snow gauge data. Moreover, the results of simulation with the SRM model showed that the model could simulate the snow runoff in the studied region. As the main purpose of the study, the effect of temperature and precipitation in future periods was well stated considering the uncertainty of CMP15 series models and scenarios. The results of temperature changes indicated an average increase of 1.8 C. the results of precipitation also indicated an average decrease of more than 5%. However, decreasing precipitation in the cold months of the years had been predicted severely so that the reduction of precipitation in February was of utmost importance for feeding the snow cover and rivers, which had been estimated to be 20%. This happened while increasing precipitation was mainly related to the hot months of the year whose amount was insignificant and didn`t have that much effect on the runoff. Accordingly, due to the increases in temperature and decreases in precipitation in cold seasons, the results of runoff simulation have indicated a 24% reduction for 2016-2017 and a 29% reduction for 2017-2018 water years.
Climatology
Hossein asakereh; Seyed Abolfazl Masoodian; Fatemeh Tarkarani
Abstract
Introduction
According to previous investigation and examining climatic elements, the hypotheses of global warming and consequently, global climate change is confirmed by majority of climatologists society around the world. The global changes probably continue for the next decades. The changes in climatic ...
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Introduction
According to previous investigation and examining climatic elements, the hypotheses of global warming and consequently, global climate change is confirmed by majority of climatologists society around the world. The global changes probably continue for the next decades. The changes in climatic elements, by and large, categorized into two types; trends and variation. The trends refer to long term changes, whiles variations indicate vary time interval changes including oscillation, phase, jump (sift), and persistence.
Precipitation is one of climatic elements which can properly reflect chaotic behavior of climate system, and illustrate the nature of changes in the system. Trends, Oscillation, and persistence in this element are investigated in national and international scale, whilst the decadal variations as an index of climate variation can contribute to the current literature. In current study we attempted to illustrate an objective feature of precipitation characteristics and its anomalies over four recent decades by using Asfezari National Dataset (AND).
Data and Methods
In the present study, the gridded precipitation data of the third version of AND with spatial resolution of 10×10 km during the time period of 1970/3/21 to 2016/3/19 (46 years including 16801 days) is used. This dataset adopted from 2188 synoptic, climatology, and rain gauge stations and subjected to interpolation by using Kriging interpolation method. The dataset covers an area from N and E. Accordingly, a pixels cover the area for 16203 days. Consequently, the dataset includes dimensions.
General spatial features of Iran precipitation for the whole under investigation period was studied based on climatological annual precipitation. Next, the same characteristics calculated for four decades ending up to 2016/3/19. Finally, for every decade the anomalies of precipitation in compare with the whole understudy period and its previous decades calculated in order to discover the spatial pattern of decadal fluctuation in precipitation.
Discussion
General characteristics of annual precipitation
Annual mean of precipitation over Iran is 250.5 mm. Due to decline in temperature contrast and strength of fronts in the Mediterranean cyclones, as a main source of precipitation in Iran, the annual precipitation over Iran decreases from west to east, and from north to south.
The annual precipitation in 63.2% of Iran is lower than the climatic annual mean. The annual mean of precipitation in this area which generally located in east and south of the country is approximately 150.5 mm. Thus, the total precipitation in this area is equal to the total precipitation in the rest 36.8% of the country which its annual precipitation is more than the annual precipitation in the country, 422 mm. The spatial variation of precipitation is confirm by other statistics, for instance, skewness, kurtosis, the extreme threshold indices. For instance, a large part of Iran (26.73%) includes 100-150 mm annual precipitation, whiles the precipitation in 15.8% of the country reaches to 150-200 mm. Parts of northeast of Iran, and the coast of Persian Gulf and Oman Sea in the south, in addition to southern slops of Alborz mountain chain experience a precipitation amount of lower than 100 mm. In contrast to the above-mentioned dry regions, the (approximately) wet regions include limited areas for each precipitation class. For example, only 9.1% of the country characterized with 500 mm of precipitation, while the classes of 200-300, 300-400, and 400-500 comprise 20.62, 12.64, and 6.11 percents of the country, respectively.
Decadal variation of precipitation
In current section the spatial distribution and statistical features of precipitation in each decades was illustrated. The following list includes our finding of statistical - graphical analysis of precipitation in four successive decades:
1) The difference between spatial mean and median of annual precipitation increased from the first to the last decades. The increasing in this characteristic refers to increase in spatial asymmetrical distribution of precipitation over the country.
2) A comparison between spatial distribution of precipitation maps showed that generally, the areas experienced precipitation above the decadal and whole period average are decreased from the first and last decades.
3) The increase in spatial skewness from the first decade to the last decade is another evidence of increasing in precipitation spatial differences.
4) The last but not the least finding is the changes in the extreme threshold indices. From the first to the last decade, the range of 10th and 90th percentiles have increased.
Conclusion
Previous studies depicted that the amount of Iran precipitation has decreased over recent decades. In order to investigate the role of each decade in the decreasing values, the gridded precipitation data of the third version of AND with spatial resolution of 10×10 km during the time period of 1970/3/21 to 2016/3/19 (16801 days) is used. General spatial features of Iran precipitation for the whole under investigation period was investigated based on climatological annual precipitation. Next, the same characteristics calculated for four decades ending up to 2016/3/19. Finally, anomalies of precipitation in compare with the whole understudy period and previous decades calculated in order to discover the spatial pattern of decadal fluctuation in precipitation.
Our finding showed that by and large, precipitation has decreased over recent decades. The changes has been more pronounced in southern and northern coastal area, western slopes of Zagros mountain chain, and northern slopes of Alborz mountain chains. Previous researchers attribute these changes to changes in humidity advections in recent years.
Climatology
mehran fatemi
Abstract
Introduction One of the climatic factors that occur during the cold period of the year in most parts of the country is the phenomenon of cold and glacial. Glacial begins when the temperature decreases and falls to a certain critical threshold, and with the effects it has on the earth's surface, it affects ...
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Introduction One of the climatic factors that occur during the cold period of the year in most parts of the country is the phenomenon of cold and glacial. Glacial begins when the temperature decreases and falls to a certain critical threshold, and with the effects it has on the earth's surface, it affects human life as well as construction activities and the yield of horticultural crops. This complication occurs on fruit trees in winter or early spring and causes a lot of damage. The glacial phenomenon not only endangers the natural life of all living things but also plays an important and decisive role in economic, environmental, and development matters such as roads, dams, and bridges. Glacial is very important in different stages of growth of agricultural and horticultural crops. Because if happen, it leads to production constraints. Glacial means zero temperatures or less than zero. Likewise in terms of technology for agriculture, in the event of thin ice crystals formation on the surfaces with sub-zero temperatures, the temperature of the surface air layer is reached above the dew point. In terms of farming meteorology, glacial is related to the low-temperature alteration which causes damage to the tissues of the plant. Glacials can be classified based on the severity, duration, and timing of occurrence. The classification based on the severity is the power of energy distribution components, which usually are measured based on average temperature, minimum, and average of zero and sub-zero and the lowest temperature of the minimums. The beginning and end dates of the glacial period are important from an agricultural point of view. The first glacial that occurs at the beginning of the glacial age is called early autumn glacial. In the autumn, glacial earlier than normal damage to actively growing branches. The last glacial that occurs at the end of the glacial period is called the late spring glacial. Fruit trees are increasingly susceptible to glacial damage from the time flower buds open, during flowering to the stage of small green fruit. To minimize glacial damage in susceptible areas, full knowledge of the frequency, persistence, and timing of glacial events is essential. To measure the risk of glacial, the recorded data of the minimum air temperature in meteorological stations are used. From a meteorological point of view, glacial occurs when the surface temperature and vegetation on it decrease to less than zero degrees Celsius. Materials and Methods In the current study, the minimum daily temperature statistics of 10 meteorological stations during a period of 17 years (2001-2018) have been used. To analyze the frequency of glacial occurrences for each year, the time of occurrence of the first early autumn glacial and the last late spring glacial was obtained. To convert the data into processable numbers based on the Julian days, each date is assigned a number. Based on this, the September 23 (1st of Mehr) was considered No. 1 and August 23 (31st of Shahrivar) in normal crop years was considered 365, and based on this, the number of the first glacial (early autumn cold) and the last glacial (late spring cold) were identified separately based on the stations during each crop year. Days, when the temperature was less than zero degrees Celsius, were extracted as glacial day and glacial at 5 weak temperature thresholds (temperature between zero to -1.9 degrees Celsius), mild (temperature between -1.9 to -3.9 ° C), moderate (temperature -4 to -5.9 ° C), severe (temperature between -6 to -9.9 ° C) and very severe (temperature -10 ° C and Less) was studied (adapted from Qalehri, 2018: 16). Using SPSS software, the best statistical sequence was obtained to calculate the start and end dates of glacial at different probability levels. The results indicated that most of the selected statistical series have a normal distribution. ArcGIS software was used to zoning the time of onset and end of glacial and to prepare many maps of glacial occurrence. Result and discussion The spatial distribution of the beginning of the glacial in the province follows the topographic state of the region and begins earlier in the southern and southeastern parts of the province. In some parts of the southern and southeastern regions, due to the high altitude of the region and being located in the mountainous areas, early autumn glacial occurs earlier, such as Garizat station, and occurs from November 6 to 12 (Aban 15 to 21). At Bafgh station, the beginning of autumn glacial occurs from November 13 to 19 (Aban 22 to 28). At Marvast, Meybod, and Abarkooh stations, the starting date of glacial is from November 20 to 25 (Aban 29 to Azar 4). The date of occurrence of early autumn glacial in Herat and Robat stations is November 26 to December 2 (5 to 11 Azar). The beginning date of glacial in Mehriz, Yazd, and Aqda stations is from December 3 to 9 (12-18 Azar). The beginning date of glacial based on different probabilities in Garizat stations with a probability of 30%, is November 3 (12 Aban), with a probability of 50% is November 6 (15 Aban), with a probability of 70%, November 9 (18 Aban), and with a probability of 90%, November 14 (Aban 23), as the earliest start date of autumn glacial. At Yazd station, with a probability of 30%, the first glacial has occurred on November 23 (2 Azar), with a probability of 50%, December 4 (Azar 13), with a probability of 70%, December 8 (Azar 17) and with a probability of 90% on December 24[Ma1] (3 Dey). The glacial at Bafgh station will end sooner on January 8 -17 (18-27 Bahman). Glacial in central and southern areas such as Mehriz, Yazd, Aqda, and Herat will end on February 18 to February 26 (Bahman 28 to Esfand 7). At Meybod, Abarkooh, and Robat Posht Badam stations, the end date of the glacial is February 27 to March 9 (Esfand 8-18). At Marvast station, the end of the glacial occurred on March 9-19 (Esfand 18-28). In the highlands, including Garizat station, the glacial starts earlier and ends later, so the glacial season is longer in these areas and the growing season is shorter, March 20-30 (Esfand 29 to Farvardin 10). The end date of glacial at Bafgh station with a probability of 30%, occurs at January 23 (Bahman 3), with a probability of 50%, February 12 (Bahman 23), with a probability of 70%, February 25 (Esfand 6) and with a probability of 90%, March 5 (Esfand 14). At Garizat station, the last glacial occurs with a probability of 30% on March 26, (Farvardin 6), with a probability of 50%, on March 29 (Farvardin 9), with a probability of 70% on March 31 (Farvardin 11), and with a probability of 90% on April 8 (Farvardin 19). The spatial distribution of the number of glacial days on the threshold zero shows that southeast areas including Garizat station have the most frosty days (1685 days) and Bafgh (483 days), Mehriz (484 days), Robate Posht Badam (518 days), Yazd (463 days) and Aqda (362 days) have the lowest number of glacial days during the statistical period (2001-2018). Spatial distribution of glacial occurrence at temperature thresholds of (0 and -1.9) have the highest number of glacials and the central and northern regions have the lowest number of glacials. Therefore, the Garizat station (467 days) has the highest amount of glacial, and Bafgh and Aqda stations have the lowest amount of glacial at this threshold. Likewise, on the threshold (-2 to -3.9), the southeastern and northwestern regions have the highest number of glacial and the northern and central regions have the lowest number of glacial. So, Garizat, Abarkooh, and Meybod stations have the highest amount of glacial and Mehriz, Yazd, Bafgh, Robat-e Posht Badam and Aqda stations have the lowest amount of glacial at this threshold. Conclusion Studies conducted between the start and end dates of glacial and the height of selected stations showed that there is a significant relationship between altitude and the date of occurrence of early autumn glacials. As altitude increases, glacial begins sooner. This fact designates that early autumn glacials happen earlier in the mountains than in the plains. The glacial onset map shows that in the plains of the province, the time of the first glacial is about a month later than the highlands of the province. In late spring glacials, the relationship between altitude and the end of the glacial is direct and by increasing the altitude, the date of the last spring glacial is delayed. This indicates that in the plains, the glacial period begins later and ends earlier, in other words, the glacial season in these areas is shorter and the growing season is longer. Conversely, in the highlands, the length of the glacial increases, and the length of growth decreases. This is significant from an agricultural point of view. Besides, the frequency of glacial in the southern and southeastern regions is higher than in the northern and northeastern regions, which has a significant relationship with altitude. The results of the analyzes showed that the Garizat station has the most glacial at all thresholds in the studied period. The lowest amount of glacial days is related to Bafgh, Aqda, and Mehriz stations in the temperature threshold (less than -10). The spatial distribution of the occurrence of glacial at different temperature thresholds also showed that in general, the southern and southeastern regions of the province have the highest frequency of this phenomenon, and as we move to the north of the province, the frequency of glacial decreases.
Climatology
kobra baharvandi; Ali Mohammad Khorshiddoust; Mojtaba Nassaji Zavareh
Abstract
Introduction The purpose of this study is to analyze the temperature trend in Khorramabad station, and an attempt has been made to provide a suitable method to ensure the accuracy of the data, which is the first time that this station is used. The statistical years (2013-2013) have been that the data ...
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Introduction The purpose of this study is to analyze the temperature trend in Khorramabad station, and an attempt has been made to provide a suitable method to ensure the accuracy of the data, which is the first time that this station is used. The statistical years (2013-2013) have been that the data in these years have been recorded in a coherent and regular manner and this data has been easier to access. In view of the above, this study intends to identify and modify possible inhomogeneity as much as possible in the first stage while examining the accuracy of data homogeneity before analyzing the trend. In the second stage, the analysis evaluates the trend of minimum temperature over 30 years. Data and Method The SNHT (Standard Normal Homogeneity Test) method is one of the most common methods for examining the homogeneity of temperature and precipitation data, which has been used by many researchers around the world. This method has been proposed by various researchers and for more accurate detection of atmospheric fluctuations from heterogeneity by non-atmospheric factors, this test is used by considering the reference series. In this method, the tested time series is based on the stability of the difference of parameter d between the temperature in the tested station and the reference series. Heterogeneity in the test series is revealed by changes in the d series. To reduce the spatial effect on temperature values, the relation (t ˍˍ t is used, where t is the average temperature value and r is the correlation coefficient between the subject and reference station (for example (t io ˍˍ to) and t jr ˍˍ tj)), respectively, temperature values It is in the test station and in each reference station. The parameter d in each time step i for k reference station is calculated based on the following equation. This test is performed by two methods of absolute standard normal homogeneity and relative normal standard homogeneity. Here, considering that only the time series of a station is examined, the absolute standard normal homogeneity method is used. In fact, this method is a necessity for climate research that must be done before any calculations, and after confirming the homogeneity of the data by the test, the rest of the research studies can be continued (Nassaji Zavareh, 1392: 58). Results and Discussion In this study, due to the lack of adjacent stations during the statistical period in the region, the absolute standard normal homogeneity method has been used to examine the homogeneity of the data. This test was used for monthly time series. The test results showed most of the monthly time series were homogeneous. In a number of months, heterogeneity was observed in the time series. Because the type of test used was an absolute test and the metadata did not confirm this heterogeneity, these heterogeneities could be attributed to natural atmospheric fluctuations. This result is consistent with the research of Peterson et al. (1998). Analysis of the plotted graphs shows that there is no heterogeneity based on this test, which is also confirmed by the metadata in Table (4). Because the meteorological station of Khorramabad city has been moved from the city centre to outside the city since 1981. Therefore, the data recorded from 1981 onwards are standard and acceptable. In this study, the length of the statistical period under study begins in 1984 and ends in 2013. Data homogenization results were performed by absolute homogeneity test for each month separately for 30 years. Altogether two results are obtained from the analyses: Two results are obtained: 1- The temperature of the minimum statistical period of thirty years has acceptable homogeneity. 2. Some inhomogeneity observed in April, May, June and July are due to weather conditions. Conclusion 1. The results of the SNHT test on the data showed that a series of heterogeneity is seen in the data process over 30 years, but it is not related to the displacement of the station, and it is related to the weather conditions. 2 - The results of non-parametric I-Kendall test on the data and during the 30 years of the statistical period showed that the value of T-statistic is significant in most months and the trend is also positive. 3- According to the T-statistic of the non-parametric method I-Kendall, the trend of glacial intensity in Khorramabad station is decreasing, i.e. the days we had in this glacial station are decreasing and it shows the fact that the weather in Khorram-abad city has an increasing trend. The results of this study are consistent with the research of other researchers such as Rahimzadeh (2011), and Shiravand et al. (2010). In relation to answering the research questions, it should be stated that this research, according to its title, is an analysis of the trend of minimum temperature and frosty days during 30 years. It is hoped that in other studies, researchers will address this issue in a more comprehensive manner, and these responses have only been proven using the statistical methods studied, if in addition to other atmospheric factors, factors such as The heat island in the city centre, the reduction of green space, the increase of carbon dioxide, etc. have always affected the climate of different regions. Therefore, all factors should be considered in the study of climate change in a region, which in this study, according to its title, is not an opportunity to research and describe the mentioned factors.
Climatology
Zeynab Jawanshir; Khalil Valizadeh Kamran; Ali Akbar Rasuly; Hashem Rostamzadeh
Abstract
Introduction Water management has always emphasized the need to abandon water storage in reservoirs and pursue a policy of limiting water consumption. Spatial-spatial information on evapotranspiration helps users understand the evacuation and depletion of water due to evaporation and establish the relationship ...
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Introduction Water management has always emphasized the need to abandon water storage in reservoirs and pursue a policy of limiting water consumption. Spatial-spatial information on evapotranspiration helps users understand the evacuation and depletion of water due to evaporation and establish the relationship between land use, water allocation, and water consumption. Evapotranspiration is the second element of the water cycle (after precipitation) and its accurate estimation on a regional scale is necessary to design appropriate management strategies. Evapotranspiration is a function of the amount of energy available for vegetation and its exchange. Because of this dependence, it can be estimated using the principle of energy conservation. Due to the limited number of meteorological stations in the country and the high cost of collecting ground data, the cost-effectiveness of the use of satellite data is one of its advantages, and the possibility of retrieving data from all levels of the region at one time is its next advantage. Having timely information makes horizontal monitoring of meteorological and environmental parameters possible. The ability of remote sensing to measure some terrestrial parameters has had an important effect on estimating actual evapotranspiration. The SEBAL model is one of the remote sensing algorithms that calculate plant evapotranspiration based on the momentary energy balance at the level of each pixel of a satellite image. The study area of the current research was the eastern cities of Lake Urmia. The reason for studying this section was the impact of recent droughts on these areas and the reduction of surface and groundwater, which has increased the need to manage water resources in these areas. Methodology In the first step of radiometric corrections, the amount of spectral radiance in the thermal band and at the next step, the reflectance in the visible bands, near-infrared, and short-wavelength infrared bands were calculated. As mentioned above, in the SEBAL model, actual evapotranspiration is calculated through satellite imagery and meteorological data is calculated using the surface energy balance. When satellite imagery provides information for its transit time, SEBAL calculates the instantaneous evapotranspiration flux for that time. Landsat 8 images for 2017-2016-2014-2013 years and meteorological data such as Minimum temperature, maximum temperature, dew point temperature, evaporation pan data, sunny hours, and wind speed were analyzed using ENVI 4.8 - Excel 2013- Arc GIS 10.3 software. Results and Discussion SEBAL is an image processing model that measures evapotranspiration and other energy conversions on the Earth's surface using digital data measured by remote sensing satellites that emit visible, near-infrared, and thermal infrared radiation. This method uses surface temperature, surface reflection, and normalized plant differential index (NDVI) and their internal relationships to estimate surface fluxes for different types of land cover. In this section, using the values obtained from latent heat flux and evaporation heat flux, first, the amount of instantaneous evapotranspiration for each pixel was calculated. Then, using Ref_ET software, the total 24-hour evapotranspiration was calculated and the daily evapotranspiration rate was obtained for the whole image. Conclusion The results showed that there was a good correlation between the values estimated by the remote sensing algorithm (SEBAL) and the FAO-Penman-Monteith method as well as the evaporation pan method. The difference between the amount of SEBAL and the FAO-Penman-Monteith method in the reference plant was less than 4.21 mm/day; the largest difference was related to the 22nd of October. In total, SEBAL and Penman-Monteith methods had an average absolute difference of 4.28 mm/day. According to the results of this study, it can be observed that using the SEBAL model, the actual evapotranspiration and water needs of crops and even orchards and rangelands can be calculated on a large scale. This case could prove the suitability of this model for estimating actual evapotranspiration at different levels of the farm and irrigation networks. Therefore, remote sensing has a very high potential to improve the management of irrigation resources in very large areas using various algorithms and providing an estimate of the amount of ET with minimal use of ground data. Using remote sensing technology and GIS, acceptable results can be obtained in estimating the actual evapotranspiration rate, especially in large areas. If the parameters of the energy balance equations and Penman-Monteith could be calculated from satellite images spatially, with a suitable plant coefficient, the two methods would have similar results in estimating the rate of evapotranspiration. Using this method, the plant coefficient, which is one of the important factors in calculating the evapotranspiration of plants, can be accurately determined.
Climatology
Saeed jahanbakhsh; saeideh ashrafi; Hosein Asakereh
Abstract
Introduction Cyclones constitute one of the major factors determining climatic conditions, especially precipitation in the middle latitudes. Changes in the properties of cyclones in a region may lead to variations in the precipitation conditions of that region. Therefore, studying major aspects in cyclones ...
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Introduction Cyclones constitute one of the major factors determining climatic conditions, especially precipitation in the middle latitudes. Changes in the properties of cyclones in a region may lead to variations in the precipitation conditions of that region. Therefore, studying major aspects in cyclones can clarify variations in precipitation conditions. In this research, changes of cyclones associated with precipitation in the Zard Rud basin (a Sub-basin of Jarahi basin in khozestan) has been reviewed decadal during a period ranging from the hydrological year of 1976-1997 to 2013-2014. In this research, daily precipitation maps during the studied period (13879 days) by using kriging method has been provided. Data and methods So the long-term precipitation mean of all days were extracted and by using 50 percentile, rainfall season detected. Upon identifying the precipitation season, Cyclones detected for this period. For identifying cyclones 1000 hPa hourly maps (NCEP/NCAR) were utilized. Two conditions were used to detect available cyclones: (1) the height values in each pixel of the 1000 hPa height map should be smaller than those of it 8 neighboring pixels and (2) the gradient mean of the height of the selected pixel and its 8 neighboring ones that was equal or smaller than 100 m/1000 km was regarded as the cyclone center. After identifying the cyclones on the map, the center of each cyclone was identified in consecutive maps to track the cyclone path. It was hypothesized that precipitation in the basin of the Zard Rud would be affected by the cyclones dominating the area as well as the trough of the cyclones that were far from the area, but could influence the region. Discussion Cyclones associated with precipitation in the basin were identified in the light of the presence of the cyclone or its troughs over the region during the occurrence of a precipitation. The results show that The extent of the area and frequency of cyclones in studied decades and consequently frequency of cyclonic rainy days and annual cyclonic precipitation in Zard Rud basin have decreased. Reduction in the frequency of cyclonic precipitations can be attributed to the place where the cyclones are formed. Indeed, in comparison with the past, a larger number of cyclones are formed over Saudi Arabia and Iraq, a phenomenon which has led to the entrance of dry or less humid air into the studied region. Masoudian (2012: 15-33) also indicated that a cyclonic center was formed over Iraq. Results Longitudinal extent area of cyclones decreases from 72.5˚ in first decade to 55˚ in fourth decade and Latitudinal extent decreases from 30˚ in first decade to 25˚ in fourth decade. Annual review on cyclones entry point to Iran show that minimum latitudinal extent from 1986-1987 hydrological year and maximum latitudinal extent from 1991-1992 hydrological year had fluctuation. So that, in 2011-2012 hydrological year, latitudinal extent of cyclones entry to Iran has reached the narrowest of its paths. Examining mean differences in the cyclone frequency of two halves of period (first half: 1976-1977 to 1994-1995 hydrological year and second half: 1995-1996 to 2013-2014 hydrological year) also revealed a noticeable shift in cyclones frequency. Result of surveying of cyclonic precipitation show that cyclonic total precipitation decreased during the studied decades. However, frequency of cyclones is less than first decade but second decade has the maximum amount of precipitation. It is may resulted of continuity of cyclones in this region. Taken together, a change was observed in geographical extent and frequency of cyclones associated with precipitation in the Zard Rud basin, which in turn affected precipitation in the area
Climatology
Yagob Dinpashoh; Saeid Jahanbakhsh-Asl; Leyla Mosavi Jahani
Abstract
Introduction One of the standard models for estimation of ET0 that accepted by all hydrologists and climatologists is the FAO Penman-Monteith (FAO56PM) method. Although this model is accurate in ET0 estimation, however, it has some limitations. The main limitation of this method in in its need for various ...
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Introduction One of the standard models for estimation of ET0 that accepted by all hydrologists and climatologists is the FAO Penman-Monteith (FAO56PM) method. Although this model is accurate in ET0 estimation, however, it has some limitations. The main limitation of this method in in its need for various meteorological data, including the solar radiation, air temperature, relative humidity, dew point temperature, wind speed and actual vapor pressure. Unfortunately, all of these parameters are not readily available in all the conditions. In this regard, many researchers interested to find a simple method for accurate ET0 estimation (Sentelhas et al., 2010; Dinpashoh, 2016; and many others). Based on our best knowledge there is no comprehensive study conducted in Urmia Basin for finding a simple and accurate method that needs less weather parameters for ET0 estimation. Therefore, the main aim of this study is estimation of ET0 that needs less weather parameters in Urmia Lake basin. Materials and Methods The area under study is the Urmia Lake Basin, located in North-West of Iran. This basin is approximately lied between the 35⸰ 40´ E to 38⸰ 29´ E latitudes and 44⸰ 07´ to 47⸰ 53 longitudes. The area of this basin is about 51700 km2 which is equal to about 3.2 percent of Iran's area. Data used in this research are the daily recorded values of maximum air temperature, minimum air temperature, wind speed at 10 m height, relative humidity, sunshine duration, and some geographic information such as altitudes, latitudes and longitudes. The nine stations were selected from different points of the basin in this study. The FAO56PM method (Allen, 1998) was selected as the bench mark for ET0 estimation in all the stations. In this method the following equation was used for ET0 in the chosen sites. (1) where ET0 is the reference crop evapotranspiration (mm/day), Rn is the net solar radiation at crop surface (MJ m-2 day-1), G is the soil heat flux (MJ m-2 day-1), T is the mean air temperature at 2 m height (°C), u2 is the wind speed at a 2 m height (m/s), the term (es-ea) is the saturation vapor deficit (kPa), Δ is the slope of the vapor pressure curve at the point of air temperature (kPa/°C) and g is the psychometric constant (kPa/°C). In order to convert U from 10 m height to u2 the following equation was used (Nandagiri and Kovoor, 2005; Sentelhas et al., 2010; Dinpashoh et al., 2011): (2) where Uz is the wind speed (m/s) at z m height, and zw is the height (m) at which wind speed measured. In this study, in order to find an alternative model, which uses less weather data in estimation of ET0 the three empirical models namely Hargreaves (HG), Kimberly Penman (KPM), Priestly Taylor (PT), and Multivariate Linear and non-linear regression were used. Evaluation of the models performed using the three metrics, coefficient of determination (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE). Results and Discussion Results showed that, the median of the R2 values for KP was more than 0.986. The median of the R2 values for PT and HG models were found to be equal to 0.902 and 0.40, respectively. The median of RMSE for HG model was about 0.9 (mm day -1). This value for KPM and PT models were about 1.3 and 2.1 (mm day -1). The median of MAE for the selected stations for KPM was less than 1 (mm day -1). This value for HG was equal to 0.7 (mm day-1) and in the case of PT was more than 1.5 (mm day -1). Therefore, considering the MAE values and RMSE, the HG model was detected to be the suitable method foe ET0 estimation in Urmia Lake basin.
Climatology
Ali Ghasemi Beqtash; Ali Mohammad Khorshiddoust; Khalil Valizadeh Kamran
Abstract
Introduction Today, there are many factors involved in air pollution. PM10 is one of the significant elements influencing air pollution in the city. Due to their fineness, these particles can travel to high altitudes and long distances. The metropolis of Tabriz is known as one of the polluted cities ...
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Introduction Today, there are many factors involved in air pollution. PM10 is one of the significant elements influencing air pollution in the city. Due to their fineness, these particles can travel to high altitudes and long distances. The metropolis of Tabriz is known as one of the polluted cities whose air pollution is caused by burning a huge amount of fossil fuels, lack of green space and topographic and climatic conditions. Given that the purpose of synoptic studies is to explain the key interactions between the atmosphere and the surface environment, and synoptic climatology pursues a major goal and that is to find the relationship between atmospheric circulation and the surface environment. Given the importance of the phenomenon of dusty air pollution and on the other hand its widespread spatial expansion in recent years in the northwest, the need for this research was felt more than ever; Therefore, in this study, suspended particles in the atmosphere have been analyzed as one of the most important air pollutants in Tabriz Materials and Methods In order to investigate the effect of active pressure patterns on pollution in Tabriz metropolis, the synoptic analysis method was used. In order to influence the meteorological conditions on increasing and decreasing pollution, pressure gauging meters have been used in connection with the main PM10 pollutant. To achieve this goal, the average daily data of PM10 in the years 1992-2010 in Bagh Shomal station and meteorological data of Hamidid station in Tabriz have been used. The method was as follows: the data were first entered into Excel software and based on the standard table of air quality, the standard limit of pollutants was determined. Extreme contaminated days were filtered and extracted by Excel. Polluted days with dangerous conditions on March 15-16, 2009 and to May 6 the same year. Then using the surface pressure data, the level of 500 hPa of pressure patterns on the infected far days were analyzed. The study of air quality index showed that the highest number of polluted days occurred in 2008 and the lowest number of dangerous polluted days occurred in 2006. In addition, the highest number of dangerous polluted days occurred in March, May, April and June. The results of the study of synoptic patterns show the existence of a weak pressure cells at the level of 500 and the dominance of a strong low pressure system at ground level and the distribution of temperature along with the hot core over the region. Also, the effect of the condition of the upper levels of atmosphere on the contaminated days by drawing synoptic maps of 500 hPa on the polluted days were examined. The Lund correlation method was used to select the representative days of the groups obtained from the classification of atmospheric pressure data. In this way, to select the representative day, the day that has the most similarity with the most number of group days was selected. Findings and Discussion The correlation coefficient represents the degree of similarity of the patterns of the two maps with each other. To do this, a certain threshold correlation coefficient must be accepted. The value of correlation coefficient in such cases typically varies between 0.5 to 0.7. Representative days were extracted based on a threshold of 0.5. Thus, the day that has a correlation coefficient of 0.5 with more days was selected as the representative day. The 500 hPa pattern, which has changed the climate of Northwestern Iran, is a Rex-type blocking system. Such a system is called lateral lifting Rex. After re-combining the western current in the east of this system, hot and dry conditions are applied to the area under their coverage. From the Northwestern region of Iran, in the impact basin of the low eastern part of this Rex system, which is mentioned outside the combined flow; Therefore, the unstable conditions in the study area are due to the positive rotating tawny wind of this arrangement from the lateral Rex system. In the case of west and east winds, the type of flow is important because their flow can be orbital or meridional. The wave motion of the winds in the meridional direction causes cold air to accumulate and fall inside the vessels within the higher latitudes to the lower latitudes, and vice versa, in the ridges, the warm air of the lower latitudes ascends to the higher latitudes. Orbital component maps show the direction of the wind (if the direction of the wind is negative and if it is positive in the direction of the west) and the speed of the orbital winds. The meridional component shows the wind speed in the north direction (if the wind speed values are positive) and south (if the wind speed values are negative). The wind map on the first day of pollution shows that the current The wind blows in a counter-clockwise direction in the low-lying center of the Mediterranean and at the same time in Northwestern Iran it moves in a counter-clockwise direction (anticyclonic) and increases pollution in the metropolis of Tabriz, but on the last day it gets west-east and The severity of pollution in Tabriz metropolis is gradually decreasing. Conclusion Given the importance of the phenomenon of dusty air pollution and on the other hand its widespread spatial expansion in recent years in the Northwest, the need for this research was felt more than ever; Therefore, in this study, suspended particles in the atmosphere, which is one of the most important air pollutants in Tabriz, has been analyzed. Examination of the air quality index of Bagh Shomal station in a period of study showed that the highest number of polluted days occurred in 2008 and the lowest number of dangerous polluted days occurred in 2006; but based on the persistence index and the average, days polluted with the dangerous condition of suspended particles were analyzed. According to the air quality index, the highest number of dangerously polluted days occurred in 2008 and in March, May and April. The hot core is on the area. Also, the effect of the condition of the upper levels of atmosphere was studied by drawing synoptic maps of 500 hPa on the polluted days. From the polluted middays, the two time periods of March 15 to March 17, 2008 and May 15 to May 17, 1988 were analyzed due to the continuity of the three days and the results indicated that there was a direct correlation between airborne synoptic circulation patterns and the polluted days in Tabriz. The main source of dust entering the metropolis of Tabriz during two periods with severe pollution of the deserts of Central Asia and Afghanistan. In addition this study showed that high air pressure, especially in the morning in autumn, causes an increase in the density of pollutants on the ground.
Climatology
mehdi asadi; Ali Mohammad Khorshiddoust; Abbas Ali Dadashi Roudbari
Abstract
Introduction As the stations measuring precipitation continuously are not regularly available, the best solution should be to investigate the points without statistics using optimal methods. Among these methods, we can mention geostatistical methods. Geostatistical methods have been approved as appropriate ...
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Introduction As the stations measuring precipitation continuously are not regularly available, the best solution should be to investigate the points without statistics using optimal methods. Among these methods, we can mention geostatistical methods. Geostatistical methods have been approved as appropriate ways for studying precipitation data and estimating precipitation regions. Results of many studies have shown that geostatistical techniques are more accurate than conventional interpolation methods. Statistical context can also be used for precipitation variability. Accurate estimation of the spatial distribution of precipitation requires a dense and regular cell network. The spatio-temporal variation of precipitation is one of the most important issues of applied climatology, so the main purpose of this study is to monitor the spatio-temporal variation of precipitation in Iran in seasonal context by the application of the mentioned techniques. Data and Methods In this study, the common statistics of 125 synoptic stations in the country with the statistical period of 30 years (1980-2010) have been used. Also, the station data were generalized to the 15 km cell spaces using the Kriging interpolation method in ArcGIS 10.2.2 software. To speed up the computational process, the capabilities of GS + software were used to fit the variogram, and ArcGIS software was used to map the precipitation regions of the country. In order to study the pattern of precipitation, spatial autocorrelation techniques (local Moran and global Moran) were used. Also, the skewness coefficient (G1) and the peak degree coefficient (G2) were calculated separately for each of the months studied. Cluster and non-cluster analyses and hot spot method were used to study the patterns and spatio-temporal variations of precipitation. Cluster and non-cluster analysis, also known as Moran local Anselin index is an optimal model for showing the statistical distribution of phenomena in space (Anselin et al, 2009: 74). For cluster and non-cluster analyses for each complication in the layer, the value of the local Moran index score, which represents the significance of the calculated index, was also calculated. Results and Discussion The value of the global Moran index for all 4 studied seasons and the annual total is above 0.95, which indicates the pattern of high clusters of precipitation in the country at the level of 95 and 99%. However, the highest Moran index in the world with a value of 0.970356 is related to the winter. Statistics for each of the five decades studied are high, between 255 and 261. Therefore, based on global trends, it can be inferred that the annual changes in precipitation in the country follow a very high cluster pattern. Consequently, due to the high value and low value, the hypothesis of no spatial autocorrelation between data in each of the five decades can be rejected. If precipitation were to be normally distributed in space for different seasons in the country, the global Moran index would be -0.000139. Moran's spatial autocorrelation only determines the type of pattern. For this reason, to show the spatial distribution of the pattern governing the distribution of precipitation in Iran, local Moran has been used during the studied periods. In winter (36.56%) there was no pattern or in other words it lacked spatial autocorrelation. This amount increased by 1.14% for spring and reached 37.70. This amount has increased significantly in summer, so that it has increased by 47.04% compared to spring. It has reached areas with no spatial autocorrelation in autumn (41.92) and winter (36.56). LL precipitation patterns have been distributed in the five studied periods with values of 36.53, 0, 34.64, 35.31 and 38.29% in the country, respectively, and in the form of nationwide spots in the eastern, southeastern and central regions. Precipitation values with negative spatial correlation in summer had the highest value (84.74%) and the lowest annual average (35.06%). However, values with high rate or positive spatial autocorrelation in all five studied periods were limited to the northern regions of the country, the highlands of Alborz, Zagros and had significant fluctuations in some parts of the country. Local Moran Anselin statistics have been able to well determine the process of precipitation (Masoudian, 1390: 97) and the era of windbreak slopes as well as adjacent areas with climatic contrasts such as north-south slopes of Alborz and slopes of east-west Zagros. Due to the complexity of precipitation patterns in the country, spatial statistics can well explain precipitation patterns. The general results of this statistic (local Anselin Moran) indicate that the amount of rainy areas in the country has been reduced during five study periods. It should be noted that most of these reductions were related to the Zagros region, the southeast of the country and the northern regions of Khorasan. Conclusions Iran has special conditions in terms of precipitation due to its vastness with respect to latitude and longitude, the configuration of unevenness and exposure to air masses. The general structure of precipitation in Iran is affected by latitude, altitude and air masses, so that with the change of any of these factors, precipitation will also change. In other words, the general conditions of precipitation are a function of latitude and altitude, and other factors such as water areas and land cover, which are referred to as local factors, play a role in the formation of Iranian precipitation. In the present study, spatio-temporal analysis of Iranian precipitation has been done using a new method of spatial statistics. For this purpose, high and low clustering methods, local and global Moran, hot spots and cluster and non-cluster analyses have been used. The present study focuses on the assumption that precipitation in Iran follows a cluster pattern and the pattern of precipitation distribution is itself a function of internal and external conditions. To achieve this goal, the average seasonal and annual precipitation statistics of 125 synoptic stations in the country during the statistical period of 1980-2010 were used. Then, to apply the methods used in this research, the capabilities of GIS were used. The results of the global Moran method and the K-function of some distances showed that the annual changes in precipitation in Iran follow the pattern of high clusters. According to spatial autocorrelation analyses, the areas with negative spatial autocorrelation in all studied periods are related to the southeast, the coasts of the Oman Sea to Abadan and parts of the northeast of the country. Areas with positive spatial autocorrelation were often located on the southern shores of the Caspian Sea and the Zagros strip. In all the studied periods, less than one quarter of the country's area lacked a significant spatial autocorrelation pattern. Spatial analyses showed that Iran's precipitation patterns are divided into two precipitation spots of southern tabs (low precipitation spot LL), and Caspian coasts west and northwest (precipitation spot HH). The results also indicated that during the period under study, low precipitation spots (negative spatial autocorrelation) had much more frequency than precipitation spots.
Climatology
Hashem Rostamzadeh; majid rezaei banafsheh; Akbar hosseinnejad
Abstract
Introduction
The global warming of the Earth due greenhouse gases diffusion (GHGs) is undeniable now; over the past century, atmospheric CO2 concentrations have increased significantly and caused an increase in global temperature of 0.44 ° C compared to Pre-industrial era. The Intergovernmental ...
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Introduction
The global warming of the Earth due greenhouse gases diffusion (GHGs) is undeniable now; over the past century, atmospheric CO2 concentrations have increased significantly and caused an increase in global temperature of 0.44 ° C compared to Pre-industrial era. The Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report (AR5) shows that there is a positive correlation between the amount of CO2 and global temperature rise. Today, climate change has attracted many scientists and researchers. The reason for this is the huge impact this phenomenon has on life on Earth. Potentially, climate change can endanger drinking water supplies, food production, and sustainable development in many parts of the world, For this reason, the International Committee of Climate Change (IPCC) calls for studies on climate change at the regional and local scale. Studies have shown that the mean temperature of the Earth has increased by about 0.18 ± 0.74 °C during the twentieth century And an increase in the temperature of the 21st century is estimated to be 1.8 to 4 degrees centigrade.
materials and methods
In this study, the three-hour temperature data of the synoptic station of Tabriz for the statistical period of 67 years (2017-1951) was prepared. Using Matlab's coding, seasonal and annual time series were prepared for each synoptic. Then, in order to provide the seasonal and annual time SYNOPs for the daily and night temperatures, the data are divided into two groups of nightly temperatures (including mean SYNOPs temperatures from 00:00, 03:00, 18:00 and 21:00) and daily temperature (including average SYNOPs temperatures at 06:00, 09:00, 12:00 and 15:00).
Discussion and results
Temperature is one of the most important elements in climatic zonation and classification, and it plays an important role in the distribution of other climatic elements. Accordingly, fluctuations and temperature changes are very important. In recent decades, the applied results of temperature analysis have led to a study of its long-run fluctuations, especially in the global arena. Therefore, in this study, the temperature fluctuations of three hours (SYNOPs), night temperature and daily temperature of the synoptic station of Tabriz during the statistical period of 1951-2017 and the seasonal and annual time scale were studied.
The results of the study show that SYNOPs, (3:00 pm local time), have more severe changes than other SYNOPs, which in summer increases at 0/66 °C per decade. Most annual changes are related to SYNOP 00:00 (an increase of 0.47 °C). Seasonal variations in daily and nightly temperatures also indicate that the highest changes in the night temperature were observed in summer (an increase of 0/62 °C), and the highest daily temperature changes were observed in spring and summer (an increase of 0.3 °C) Is.
the findings of this study are largely consistent with the findings of other studies in the study area. For example, Dinpajoh et al. (1394) obtained the same results by analyzing the process of weather parameters in Tabriz, indicating an increase in the minimum, maximum and average temperature in Tabriz. The results of the study, Sari Sarraf et al. (1394), also show that in the Urmia Lake basin, the minimum, maximum and average temperature has experienced an increasing trend in the annual and seasonal scale. Jahanbakhsh Asl et al. (1396) also studied the trend of variations in the average monthly cold-year average temperature in the northwest of Iran, with the result that the average minimum temperature in most parts of the northwest is increasing. Therefore, the results of this research and previous studies indicate that the temperature in the study area is increasing. The important thing about this research and its difference with previous studies is the use and application of temperature data. So, using daily temperature data (SYNOPs), the temperature changes were dealt with, while in other studies, the average temperature or minimum and maximum temperature parameters were used, so the results of this study could be information It will provide a more accurate description of the process of temperature variation in the Tabriz Synoptic Station.
Conclusion
According to the results, it can be said that the signs of climate change in Tabriz city, especially in terms of temperature, are visible. Considering the role of temperature in increasing evapotranspiration and urban energy consumption, over the next decade, there should be solutions to better manage water and energy resources, especially heat energy during the warm season.
Climatology
Hossein Asakereh; Sepideh Barzaman; Ali shahbaee kotenaee
Abstract
Introduction
Rainfall is amongst the most important climatic elements with a lot of spatial and temporal changes; in contrast to the other climatic phenomena, rainfall features more notable movement complexity. The studies performed in this regard indicate that such a climatic element as rainfall features ...
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Introduction
Rainfall is amongst the most important climatic elements with a lot of spatial and temporal changes; in contrast to the other climatic phenomena, rainfall features more notable movement complexity. The studies performed in this regard indicate that such a climatic element as rainfall features a non-stationary behavior with a vast part of this non-stationariness being the result of the rainfall’s being influenced by the spatial properties and the complex pattern of the spatial organization causes the emergence of complex behaviors in the precipitations. The importance of the rainfall as the country’s water resource and the daily increasing reduction of the country’s water reservoirs demands the study of the rainfall’s behaviors. In the present study and by the assistance of the methods of spatial statistics, the spatial pattern of the spring rainfalls in the northwest of Iran will be elaborated.
Data and Method
The study area of the present study is the regions in the northwest of Iran (Azerbaijan-e-Gharbi, Azerbaijan-e-Sharghi, Ardabil, Kurdistan and Zanjan Provinces) and, to perform the study, use has been made of the monthly precipitation data acquired from 121 synoptic stations as well as climatological investigations and precipitation studies for a period between 1994 and 2014.
In order to perform the spatial analysis of the precipitations, use has been made of the digital map of the elevation in the environment of ArcGIS software for extracting slope and dip. In the next part and in order to analyse the spatial structure of the rainfall and investigate the degree of similarity between the data acquired from 121 station points, use has been made of the half pseudo-variance spatial correlation index. The Semivariogram has been estimated based on the arithmetic mean of the intervals.
In the present study, use was made of the longitude and latitude of every station point and the rainfall rates of every point for delineating the empirical Semivariogram for three months, namely April, May and June in the environment of Variowin Software, version 2.2; then, various theoretical models were estimated in terms of their goodness of fit and the exponential model was selected as the best model for every month.
In order to analyse the spatial factors influencing the spring rainfalls in the northwest, the balanced geographical regression model was estimated in terms of its goodness of fit with its output being the indicator or indicators influencing the occurrence of spring rainfalls according to the explanatory variables of slope, dip, elevation and latitude.
Results and Discussion
Following the investigation of the data related to April, it was made clear that the effect of the elevations on the rainfall variations is significant in this month in the entire parts of the region. The highest significant effect of the elevation has been in the central parts of the region for such a reason as the large density of the mountainous masses in this part and the passing of precipitation systems from these regions. In parts of the region’s north (north of Azerbaijan-e-Gharbi, Azerbaijan-e-Sharghi and Ardabil), the significance rate of elevation is reduced because these regions are plains and plateaus and lower in elevation than the other areas. Latitude has been found having a significant effect in the southwestern sections of the region (south of Azerbaijan-e-Gharbi, Kurdistan and Zanjan) and, in a more scattered manner, in the north of Urmia Lake and it seems that the reason for such a significance is the passing of the precipitation systems from the southern sections of the region.
As in April, the effect of the elevation on the rainfall has been also found significant in all the sections of the region in May. The highest rate of significance has been found centered in the western and central sections of the region (particularly in the central parts) and this is completely due to the existence of the mountainous air masses. Considering the gradual displacement of the western winds towards the northernmost parts of the region and the vertical irradiation of the sunlight onto the sun-facing foothills, the role of the elevations becomes more accentuated in the creation of convectional rainfalls and the regions with lower elevation would receive lower precipitations.
In June, as well, except the south-eastern section of the region (eastern half of Zanjan Province), the other regions have been found with the significant effect of elevation on the creation of rain. In this month, the conditions fit the occurrence of foothill convection in the studied area. The highest effect of the rising and falling lands on the creation of the rain has been evidenced for the north-western sections and this is in match with the path through which the western winds pass on these days; that is because the rain-causing winds are present in this section in this month and, considering the region’s elevations, cause the occurrence of rainfall. The effects of latitude in June is like those in May and the presence of the western winds and setting of the ground for the foothill convention causes rainfalls in the northern and central section of the study region.
Conclusion
Elevation has been found influential in the entire studied region on the rainfall because the high density of high grounds causes the ascension and condensation of the humid air that causes rainfall. Besides elevation, the dip also influences the rainfall in Kurdistan and south of Azerbaijan-e-Gharbi because the orientation of the foothills in this section sets the ground for the dynamic ascension of the humid air. In Ardabil and north of Azerbaijan-e-Sharghi, slope is also an effective factor. The high slope of these regions causes the acceleration of the humid air masses’ ascension. The effects of the latitude on rainfall during spring are different and mostly related to the presence of the western winds; in April in Kurdistan and in May and June in Azerbaijan-e-Sharghi, latitude has been found with the highest effect on the rainfall.
Climatology
Majid Rezaei Banafsheh; saeid Jahanbakhsh; Shoaieb Abkharabat; Aliakbar Rasouli; Mostafa Karimi
Abstract
Introduction 120-day winds of Sistan are considered as one of the significant phenomenon which has a great impact on the morphology and environment of east and southeast of Iran (Figure.1). The common region for these winds is the border of monsoon region in south of Asia which mainly has sunny and cloudless ...
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Introduction 120-day winds of Sistan are considered as one of the significant phenomenon which has a great impact on the morphology and environment of east and southeast of Iran (Figure.1). The common region for these winds is the border of monsoon region in south of Asia which mainly has sunny and cloudless weather during monsoon period. This condition is due to lack of higher humidity divergence accompanied by tangible decrease of the air on the atmosphere (Salighe, 2010). These winds are the most famous advection system in northern hemisphere whose effects are visible in eastern regions of Iran, west and south of Afghanistan, and northwest of Pakistan(Khosravi, 2008). Data and Methodology In order to evaluate the role of the winds, data network of Geopotential height of 850 hPa (hectopascal) level during a 19-year period (1993-2012) from May to the end of September, the period of 120-day winds of Sistan, were found. These data were of those revisited data of 2.5*2.5 NCEO/NCAR during 2480 days. Then, factor analysis and clustering tests were applied on data network of Geopotential height to classify map patterns (Yarnal, translated by Masoudian, 2006: 100). As a matter of fact 5 clusters were recognized in this study presented in table 1. Dynamic method was used in GrADS software in order to find humidity flux of each region in the quintuplet patterns. Discussion Northern Wind Pattern (120-day wind of Sistan) As a matter of fact 120-day winds of Sistan are a part of northern Trade winds which are the most important source of Caspian Sea high pressure. After passing east of Iran, these winds reach Oman Sea and converge with southern Trade winds. Both of them moved toward Indian Subcontinent and finally enter atmospheric monsoon circulation of south of Asia. High pressure of north of Iran is also a tongue of high pressure Azores which is extended over northern regions of Iran and Caspian Sea by Mediterranean and Black sea Basin. Both existing Gang low during hot period of a year in south of Asia and spreading, its tongues over regions of Middle East make Azores high not be able to penetrate the zone in lower levels of atmosphere (from the earth surface to thelevel 850 hPa.). As a result, Azores high has to locate in northern parts especially north of Iran. Analyzing the curves of geo-potential height, figure (2) precisely shows this phenomenon. Gang low not only is weaken among middle levels of atmospheretongue, but also lost its appearance on Iran Plateau and Arabian Peninsula. Therefore, Azores high tongue also can locate in its normal position and appear with maximum pressure on Iran Plateau and Arabian Peninsula. Figure (3) presents the order of synoptic systems in level 500 hPa. of pattern 1. It shows that Gang low has lost its nature in this level, while Azores high tongue obviously is located on Middle East, especially Iran Plateau and Arabian Peninsula. As a matter of fact atmospheric levels of Geopotential height in pattern 1 (figures 2,3, 4) reveal that as we go away from lower levels of atmosphere to middle levels of atmosphere, Gang low gradually is weaken especially over Iran Plateau and Arabian Peninsula. This situation makes Azores high tongue locate in lower latitude. However, in lower levels (earth surface to level 850 hPa.), as a tongue of Gang comes into some parts of Middle East, expanded tongue of Azores high pressure has to locate on higher latitudes than normal latitudes; on north of Iran Plateau and Caspian Sea.Pattern (2) shows the same order as pattern (1), so it will not be repeated here. In the following, the effect of 120-day winds of Sistan on humidity of the region will be investigated, thus humidity flux is calculated between levels 925-1000 hPa. 850-925 hPa. and 850 -700hPa. Figure (5) shows sum of humidity flux for aforesaid levels of synoptic pattern (1). 120-day winds of Sistan with prevailing north direction in this pattern lead to the formation of a core of humidity flux divergence in east and center of Iran and decrease humidity of the region. As previously mentioned, after passing Iran, Sistan winds reach Oman Sea and north of Indian Ocean, and converge with southern Trade winds. Both of them move toward Indian Subcontinent. In fact, convergence of 120-day Sistan winds (northern Trade winds) and southern Trade winds leads to formation of a strong core of humidity flux convergence on Oman Sea and north of Indian Ocean (figure 5). The sum and average of humidity flux convergence and humidity flux divergence in studied region are presented in table (2). Eastern Wind Pattern The other clusters (3, 4, and 5) have different order from 120-day Sistan winds which are introduced as eastern wind pattern. Unlike clusters (1) and (2), in these clusters (table 1) the wind direction is not northern; in other words, the winds blow with prevailing east direction in east and northeast of Iran, however southeast of Iran experience mild weather at the same time. As synoptic order of pressure system and humidity flux system are mainly the same, pattern (3) will be analyzed precisely. The order of synoptic systems of level 850 hPa. in pattern (3) is presented in figure (5). This map reveals that the contrast between high pressure of north and Gang low differs from northern wind pattern, as on the one hand,the strength and breadth of Gang low increase, while on the other hand the strength and breadth of Azores high tongue (high pressure in north of Iran) decrease. In fact, this condition makes most regions of Iran Plateau in lower levels of atmosphere (1000 hPa, 925 hPa and 850 hPa.) be dominated by Gang low. Besides, this order of synoptic systems eliminates 120-day wind conditions of Sistan and make eastern wind conditions in east and northeast of Iran. Since the orders of synoptic systems of levels 925 hPa. and 1000 hPa are the same as level 850 hPa. they will not be presented here. The orders of synoptic systems in middle levels are different, as in level 700 hPa. Azores high tongue comes to Iran Plateau by Arabian Peninsula (figure 7). This layer of atmosphere is a transition layer from dominance of low pressure pattern in lower layers to high pressure pattern in middle levels and upper atmosphere. Moreover, in level 500 hpa. Azores high tongue dominates Iran Plateau and Arabian Peninsula with more power and breadth. The orders of synoptic systems of clusters 4 and 5 are the same as cluster 3. The sum of humidity flux divergence and humidity flux convergence of pattern 3 are presented in figure (9). In this figure, the core of humidity flux divergence, which covers eastern half and center of Iran, is omitted and a core of humidity flux convergence covers east and southeast of Iran. It can be said that both penetration of Gang low into Iran and lack of 120-day winds provide special conditions in which the zone of humidity flux convergence in north of Indian Ocean moves to southeast of Iran leading to moisture condensation. Conclusion In this study 2 patterns of synoptic systems of warm period in east and southeast of Iran were recognized. First pattern (northern wind pattern) makes 120-day winds of Sistan (cluster 1 and 2). In contrast to Gang low tongue, when high pressure of north of Iran and Caspian Sea are in strong mode, it provides the conditions for 120-day winds of Sistan. On the other hand,in contrast to Gang low tongue increasing its influence and spread over Iran Plateau, when the aforesaid high pressure rollbacks of north of Iran and it is weakened, 120-day winds of Sistan stop and second pattern (eastern wind pattern) starts. In this pattern the winds with prevailing east direction cover east and northeast of Iran (clusters 3, 4,and 5). High pressures of Caspian Sea and north of Iran are a tongue of Azores subtropical high pressure which has to move abnormally to higher latitudes due to coming Gang low into lower atmosphere layer. Since Gang low is an inter-tropical convergence zone moving abnormally to higher latitudes in south of Asia, 120-day winds of Sistan are part of northern Trade winds which are flowing from subtropical high pressure (Azores high tongue in north of Iran) to Gang low in south of Asia (inter-tropical convergence zone). After converging with southern Trade winds on north of Indian Ocean, they move toward Indian Subcontinent. 120-day winds of Sistan exclude the entranceof moisture from Oman Sea and Indian Ocean into southeast of Iran (figure 5). However, as 120-day winds of Sistan stop, a core of humidity flux is formed on southeast of Iran providing the entrance of moisture of water areas into southeast of Iran (figure 9). Generally, weakening of Azores subtropical high will help to provide rainfall conditions in southeast by 2 ways: on the one hand, as Azores high pressure is weakened, the influence of decent factors of this high pressure air in levels 700 hPa. and 500 hPa. decreases. As a result ascent conditions are provided in the zone, but on the other hand the weakening of subtropical high pressure in lower levels of atmosphere (1000 hPa to 850 hPa.) also makes expanded Azores tongue weaken and rollback over north of Iran and Caspian Sea leading to stop 120-day Sistan winds. This phenomenon provides appropriate condition to inject moisture from Oman Sea and Indian Ocean to southeast of Iran.
Climatology
Elham Alizadeh; hossein mousavi; Jamshid Yarahmadi; Abdollah Faraji
Abstract
Introduction Climate change is one of the most important phenomena of the present century, which has created many problems and challenges both globally and regionally and nationally. In the second half of the twentieth century, global warming relative to The first half of this century has increased ...
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Introduction Climate change is one of the most important phenomena of the present century, which has created many problems and challenges both globally and regionally and nationally. In the second half of the twentieth century, global warming relative to The first half of this century has increased and it is predicted that this increase in temperature will continue in future periods, resulting in changes in the level of climatic conditions in different parts of the world. Due to the lack of atmospheric precipitation, due to the increase in temperature, the rate of evaporation has increased significantly and can greatly affect the aggravation of water shortage conditions in surface currents, especially evaporation from the surface of lakes behind dams. Percentage by evaporation leads the country to higher values (Farajzadeh and Ghasemifar, 1398). Regarding the changes in Iran's water resources in the horizon of 2100, few studies have been done and most have been case studies (Fahmi, 1393). Although the results of these studies, based on the climatic models and different scenarios used, sometimes show contradictions, so it is necessary to do more studies in this field. Methodology The present research has been done in three specific sections and the output of each section has been used as the input of the next section. In the first part, climate change in the form of precipitation variables in the study area is detected and subsequently, rainwater runoff in the Daryan catchment is simulated. Then, while identifying the characteristics of hydrological drought periods in the basin, the probability of occurrence, intensity and duration of hydrological drought periods are calculated based on the fit of different statistical distributions for different return periods in the third section. Results and discussion Climate change is one of the most important environmental problems of this century. Thus, evaluating the phenomenon of climate change and reducing its effects on both global and regional scales has attracted the attention of many researchers, planners and legislators (Yohe et al., 2007). Proper assessment of these effects requires the existence of climatic information with appropriate spatial distribution and long-term time series, as well as a thorough understanding of its future trends at the regional and local scale. Despite the fact that today the output of public circulation models (GCM) are the main sources of future climate data production. One of the most important consequences of climate change includes changes in the hydrological cycle and river flow regime of watersheds. Therefore, the present study aimed to investigate the possible effects of climate change on rainfall and runoff in the Daryan catchment area north of Lake Urmia. In this study, statistical method (SDSM) and data of CanESM2 Canadian climate model in the form of three scenarios RCP2.6, RCP4.5 and RCP8.5 in order to micro-scale the precipitation data of five synoptic stations adjacent to the sea basin and changes Its future is used. Here, the basic period (1961-2005) and future periods (2049-2020), (2079-2050) and (2080-2100) were selected. In this research, the threshold level method has been used to identify hydrological drought periods and extract its characteristics. The results of the analysis of the last 35 years of hydrological droughts in the Daryan Basin showed that 44 drought events occurred in this basin, which in total, led to a reduction in surface flow volume of about 140 million cubic meters in this basin. Conclusion The simulation results of SWAT model showed that the annual average runoff of the sea basin in the first period (2020-49) in all three scenarios increases by 3.7 and 6%, respectively, compared to the base period. While in the rest of the periods of all scenarios, runoff reduction is predicted compared to the base period. Accordingly, a decrease in surface runoff compared to the base period is predicted for five months of the year (April to August) and an increase in the remaining months. Future changes in precipitation at Tabriz station, which is the basis for modeling runoff in the Daryan basin, are not very noticeable compared to the base period, and only in the period (2049-2020) all three scenarios are predicted to increase by 5, 2 and 8%, respectively, compared to the base period. In the other periods, in all three scenarios, a decrease in rainfall is predicted compared to the base period. Results of evaluating the effects of climate change on rainfall and surface runoff in the Daryan Basin with the results of other researchers in the catchment area of Lake Urmia, including: Goodarzi and Fatehifar (2010) in the Azarshahrchai Basin, Qaderpour et al. (2016), Dariane et al. (2019) ), Sobhani et al. (2015), Goodarzi et al. (2015) and Salehpour and Malekian (2019) are consistent.
Climatology
HABIBEH NAGHIZADEH; ali mohammad KHorshiddoust; Rashid Saeidabadi; MohammadSaeid najafi
Abstract
Introduction Today, one of the most important issues in the field of climatology is air pollution and its relationship to the general circulation of the atmosphere. The atmosphere around the planet Earth is made up of gases called fixed atmosphere gases. Humans and all living things are accustomed to ...
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Introduction Today, one of the most important issues in the field of climatology is air pollution and its relationship to the general circulation of the atmosphere. The atmosphere around the planet Earth is made up of gases called fixed atmosphere gases. Humans and all living things are accustomed to this composition of the atmosphere and have adapted to it. Any changes in the quality and quantity of these elements can be considered as air pollution. Therefore, since the main cause of all changes in the characteristics of the human environment is related to changes in atmospheric pressure, so in all climate-related studies, the first step is to identify patterns of air masses. Anti-cyclonic circulation patterns, both at the Earth's surface and in the upper atmosphere, create sunny weather, leading to temperature inversion and subsequent air pollution, especially in densely populated and industrial cities. In winter, when these inversions are stronger, hot air on the cold air acts like a cap that prevents air mixing. Thus, urban areas have a strong potential to face serious problems of air pollution as a result of a combination of limited conditioning of air and emission of pollutants from high atmospheric levels. Atmosphere in terms of temperature inversion is associated with minimum air mixture and stable conditions. So the highest density in the direction of the wind extends from the source of diffusion. Methodology For the recognition and extraction of the synoptic patterns affecting the temperature inversion in Tabriz city, we initially prepared the data records on the temperature inversion for the time period of 2001-2010 by the use of upper atmosphere station data. This was followed by the utilization of digital data on sea surface pressure as daily mean from the reanalyzed data series of NCEP/NCAR in the eastern longitudes of 10°-60° and the latitudes of 10°-90° in 651 pixels of 2.5/2.5 degrees. With the PCA analysis on the data of sea surface data pressure in the days having temperature inversion, we reduced their volume and carrying out cluster analysis on the obtained components we recognized the most important atmospheric patterns and through which the map of each pattern was drawn. Results and discussion Based on the results of cluster analysis on the matrix of factor scores in this study, the occurrence of temperature inversion in the city of Tabriz is due to the domination of four consecutive patterns. The general characteristics of these patterns are as follows. 1- In general, in the hot period of the year, the high-pressure pattern of Migrant Europe is the most important system in the formation of temperature inversions. In this pattern, languages from the highlands to the western shores of the Caspian Sea are advancing, and due to the presence of a mid-level ridge, it is possible to strengthen the anticyclone core at sea level and thus create a stable atmosphere. With the dominance of the downward process of air, the stability of the earth's surface air and the possibility of inversion formation in the warm period of the year intensify. Two summer patterns, which have been associated with the establishment of a high-pressure pattern on the northwest and in some cases with a low pressure on the Persian Gulf, have caused the upheavals of this period of the year.2 - In other patterns that have occurred more in the cold season, the surface stable layer due to the penetration of the tabs of Anti-cyclonic systems including high-pressure Siberian and European Migrant Europe high-pressure is done alone or in combination and in some cases with high-pressure Migrant Europe. North pressure is also present on the map, which is exacerbated by the Convection of cold weather. Despite the process of air fall due to the dominance of the convergence region of the mid-level convergence creates deep inversions and sometimes double-layer. In these patterns, the thickness of the inversion layer is low and the temperature difference between the peak and the base is high, which indicates the acute conditions of inversion to create air pollution. This phenomenon is likely to occur in any season. But its severity, which depends on synoptic factors. Conclusion The most important factor in causing temperature inversion in most cases is how to arrange the dominant pressure patterns, In this Patterns the cold weather due to the presence high pressure system expanded in the surface with the establishment Left side of a deep trough over the region, the cold air has diffused from higher latitudes on Tabriz and strong sustainability has been created in vertical column of the atmosphere. In cases of being cause the Northern low pressure along with pressure-immigrant Europe for the spread of a cold into the region. The warm air of lower latitudes has been placed over the cold air of ground by domination of a deep ridge over the region. Therefore the intensity of stability increased and severe temperature inversion into the air near the surface formed.
Climatology
Hashem Rostamzadeh; Aliakbar Rasuly; Majid Wazifedoust; nasser maleki
Abstract
Introduction Floods are a natural occurrence that causes casualties, livestock losses and damage to buildings, facilities, gardens, fields and natural resources every year. Therefore, rainfall estimates have long been considered by researchers in various fields, and along with the advancement of science ...
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Introduction Floods are a natural occurrence that causes casualties, livestock losses and damage to buildings, facilities, gardens, fields and natural resources every year. Therefore, rainfall estimates have long been considered by researchers in various fields, and along with the advancement of science and the emergence of new technologies, many advances have been made in the methods of rainfall estimation and evaluation and validation to achieve the best method. In the last twenty years, there has been a lot of progress in rainfall estimation methods. This advancement is due to the possibility of using a lot of information from different parts of the world, better understanding of atmospheric phenomena, exchanges and atmospheric rotations, improving the performance of models, progress in various surveillance tools such as radar and satellite and computer power. The methods used to estimate precipitation, especially in the short term, have shortcomings and are generally based on numerical forecasting models or the use of empirical analyzes, which are usually not very accurate for multi-hour intervals, so the use of satellite data It has been recommended as a supplement to address this problem, and doing so could greatly help increase the accuracy of numerical models for rainfall estimates. Methodology The study used the physical properties of a cloud of five waves between 2011 and 2015. The data of the second generation of MSG meteorological satellite has good coverage on different regions of Iran. The satellite has 12 channels on the region and produces accurate products. Some of these products are in line with the physical properties of the cloud used in this study. These products are produced daily every 15 minutes and include cloud peak pressure (CTP), cloud peak temperature (CTT), cloud light depth (COT), thermodynamic cloud phase (CPH), and the volume of water in the cloud. Density (CWP) are the effective radius of cloud droplets (REFF) and cloud type (CT). Was obtained. The criterion for the accuracy of the calculations was the two MAE statistics Equation 1: Equation 2: Results and discussion In this study, TRMM satellite data was considered as control data. After receiving TRMM images in MATLAB software environment, programming was performed and precipitation data were extracted from NETCDF files. After extracting TRMM satellite data, Meteosat satellite products were prepared through the CMSAF database and their data were extracted using MATLAB software code. In the study of waves, the coefficient of determination in the GPR model was 0.72 in the experimental section and 0.77 in the training section. In the TD model, the determination coefficient is calculated in the experimental section 0.64 and in the training section 0.87. However, in the neural network model, the coefficient of determination is 0.68 in the experimental section and 0.72 in the training section. The results show a good relationship between the components studied. Investigating the Effects of Cloud Physical Properties: One of the methods for determining the effectiveness of each of the physical properties of the cloud in estimating rainfall is the sensitivity analysis method. After calculating the coefficient of determination and the error coefficient, the sensitivity of each of the physical properties in estimating the precipitation was performed by the method of calculating the sensitivity analysis. Sensitivity analysis was calculated for all waves. Calculations show that the cloud type is most effective, followed by the effective radius of the cloud droplets and then the optical depth of the cloud in the second and third positions, respectively. Among the physical properties studied, the lowest effect is related to the cloud phase. To investigate the relationship between the physical characteristics of the cloud and the amount of precipitation, five waves of pervasive precipitation were selected between 2011 and 2015. Rainfall data from the region's stations were extracted. In order to validate the TRMM data, a comparison was made between the precipitation data of the selected stations and the precipitation of this satellite. Metoost satellite products were used to extract the physical properties of the cloud. After extracting the data, the physical properties of the cloud were matched to the time scale of the data and evaluated using TRMM satellite rain as a control. Conclusion The selection criteria were such that the waves lasted for at least two days and covered the entire area. On the day of the operation, the precipitation information of the meteorological stations of the region was obtained and also the precipitation information of TRMM satellite was extracted. In order to validate the data of TRMM satellite, the information of meteorological stations was compared with TRMM precipitation and obtained the necessary correlation. In order to get a better result, the matching of numbers was done in terms of time scale. In the next step, using the meteosat satellite products, the physical properties of the cloud were obtained for all waves. Data were extracted at all stages for each pixel. Then the data correlation matrix was performed with three models of GPR, TD and MLPBR, the results of which are given in Table One. Due to the use of different models as well as the study of 8 physical properties of the cloud, the results show a high relationship between the components of the study, so that the coefficient of determination in the GPR model for the experimental and training sections was 0.7 and 0.77, respectively. These coefficients for the TD model in the experimental and training sections are 0.64 and 0.87, respectively. In the artificial network model (MLPBR), the coefficients obtained in the experimental and training sections are 0.68 and 0.72, respectively. The numbers obtained indicate a relatively good relationship between the components. Sensitivity analysis was performed. Sensitivity analysis results show that the cloud type feature has the greatest effect on precipitation and then the effective radius of cloud droplets and then cloud light depth are in the second and third positions, respectively. Among the physical properties studied, the lowest effect is related to the cloud phase.
Climatology
mohammad omidfar; Ali akbr Rasouli; Hashem Rostamzadeh; BEHROOZ SARISARRAF
Abstract
Introduction Considering the problem of continuous reduction of the water amount of urmian Lake, Identifying the distribution of rainfall in the basin area of Lake has a particular importance from the point of view of climate and hydrology. Doppler weather radar has an ability of the estimating of intensity ...
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Introduction Considering the problem of continuous reduction of the water amount of urmian Lake, Identifying the distribution of rainfall in the basin area of Lake has a particular importance from the point of view of climate and hydrology. Doppler weather radar has an ability of the estimating of intensity and the accumulation of daily rainfall with suitable spatial and diurnal resolutions. In current study, radar rainfall data, observed at the Sahand station, were evaluated with 10 synoptic weather stations data inside the Urmia Lake Basin exampling some of intensive rainfall events. The compared models show that among synoptic stations Tabriz, Shabestar, Sahand, Urmia, and Bostanabad have a best fit with radar daily rainfall productions, having high-quality conformity in northwest of the study area. In contrast, low level of agreements between two sets of radar has been observed in mountainous area. Due to the problem of continuous decreasing volume of Urmian lake water, accurate identification of the temporal distribution of rainfall can be very important from climatic and hydrological points of view. There are various ways to measure or estimate rainfall. Synoptic stations have a relatively low efficiency compared to radar and satellite due to their point and number limitation, relative to the area of the study area and other influential factors such as weather and human error. Tabriz Doppler Radar is one of the 12 radars of the National Radar Network of the Meteorological Organization of Iran, which works in the frequency band of Doppler C-type radars. The aim of this study was to investigate the efficacy and accuracy of radar-distance measurement tools in the study of heavy precipitation, which due to the infancy and lack of similar studies, the results can be used in future research. Methodology The accumulative precipitation data of synoptic stations in the studied area and the product of the daily accumulative precipitation of Tabriz Doppler radar, which is produced by the radar equation, by converting the echo-return intensity of precipitation, have been used. In this study, the data of accumulative precipitation of synoptic stations of the study area and the product of daily accumulative precipitation of Tabriz Doppler radar have been used. With the help of radar software, the product of surface precipitation intensity is produced in a 24-hour period and its temporal resolution is 15 minutes. Other product specifications such as start time, spatial resolution, and maximum distance, frequency of repetition of sent waves, name of the saved file, color scale of the data and the name of the radar site next to the product are listed. Radar accumulative rainfall on the most severe rainy day in Urmia Lake basin , the distance from the site of the radar site (concentric circles with a distance of 50 km from each other) and the location of the stations studied. Also, to compare the difference in estimation between radar and stations, error estimation indicators such as: mean error, absolute error mean, mean square error and Pearson correlation coefficient were used. Results and discussion The October 14 to 21, 2014 heavy rainfall in Urmia Lake basin has been studied by various radar products and among them 24-hour collective rain product, due to compliance with the cumulative rainfall data of stations, for 10 synoptic stations around Lake Urmia. Due to the collision of the waves with mountains, the topography of the area has a significant impact on the accuracy of radar estimation. They are considered invisible spots; these points causes a lot of errors (in some cases even up to 100%). Therefore, to compare radar data with the station, the accuracy of the separate precipitation estimate at different stations was examined. Conclusion The 24-hour accumulative precipitation comparison of the stations northwest of Urmia (for the cities of Tabriz, Sahand and Shabestar)with radar estimates on the days of heavy rains in October 2014, was highly consistent and the only difference in radar estimates on 20 and 21 days, was about 5 mm that less than Measured by synoptic stations. The correlation coefficient between the data is 0.996, which confirms the closeness of the measurement values of the two methods. The remarkable point in the chart is the significant difference and jump in rainfall on October 19 compared to other days. An examination of the graphs of the cities of Salmas and Urmia in the west and Bostanabad in the east of Urmia Lake shows less accurate but acceptable estimates of rainfall and differs. Conclusion: The comparative graph of rainfall in the Ajabshir city, despite its proximity to the radar site (50 km from the radar), shows a relatively large difference between the radar estimates and the stations. The most important cause of the error is the orientation of the southern Sahand Mountain. In moving to the more southern areas, the radar accuracy is lower, but the comparative rain chart of Ajabshir city, despite its proximity to the radar site, shows a significant difference. Overall, the results shows that: the southern regions, both due to the large distance from the radar and blocking effect of radar waves, almost all of the return waves are weakened from the targets and the radar estimates the amount of precipitation zero.
