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.
Climatology
Ebrahim Mesgari; Taghi Tavousi; Peyman Mahmoudi
Abstract
Introduction Frost is one of the most important phenomena in climatology, which is caused by changes in temperature over time. The sudden occurrence of this phenomenon at the beginning and end of the cold period can be very dangerous for the agricultural sector. Therefore, the awareness of the frost ...
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Introduction Frost is one of the most important phenomena in climatology, which is caused by changes in temperature over time. The sudden occurrence of this phenomenon at the beginning and end of the cold period can be very dangerous for the agricultural sector. Therefore, the awareness of the frost time - occurrence has long been considered by researchers (Thom and Shaw, 1958; Rosenberg and Myers, 1962; Schmidlin, 1986; Watkins, 1991; Waylen, 1988). In order to manage the reduction of the effects of this destructive climate phenomenon on the agricultural sector and the exploitation of large regional environmental capabilities, it is necessary to notice seriously the detailed study of this phenomenon and its characteristics at the land level. And this will be costly and time-consuming. Therefore, with the purpose of preventing the last two factors and at the same time achieving managerial goals, it seems necessary to accurately zoning and recognizing homogeneity and non-homogeneity between different areas in a large area. Methodology In the first step, daily minimum temperature data were adjusted based on Julius day, and the averages of the five indicators including the day of the onset of frost, the day of the end of frost, the annual number of days of frost, the length of the frost season, and the length of the growing season were extracted. In the second step, the five indicators were modeled separately with three land-climate factors, namely altitude, longitude, and latitude of the stations, using multivariate regression models. To measure the accuracy of the obtained models, four basic assumptions were examined (). Using the regression models obtained for all parts of the province, the statistical indicators of the frosts were calculated and generalized to the points without stations. Finally, using the kiriging method, each of the five frost indicators of the province was zoned. Results and discussion The correlation coefficient of three variables, altitude, length, and latitude with different frost indices was obtained by simultaneously entering these three variables into the regression model. And four basic assumptions for measuring the accuracy of the obtained models were confirmed. The earliest occurrence of the first day of frost arises between September 21 and October 27, and in the mountains of northwestern Kurdistan, especially the Chehel Cheshmeh. The latest occurrence of the first day of frost also happens in the eastern lowlands of the province between October 17 and November 23. The earliest occurrence of the last day of frost arises between March 22 and 30 in the lowlands of southeastern and southwestern Kurdistan, and the latest happens between May 24 and June 1 in the high peaks of the west and northwest of the province, such as Chehel Cheshmeh Heights at an altitude of about 3173 meters, Ketresh Mountain with a height of 2592 meters, and Vazneh Mountain with a height of 2697 meters. The highest frequency of frost is in the mountains of the region with more than 196 days and the lowest frequency is in the eastern borders of the province with less than 72 days. The northwest mountains with 235 to 248 days and the eastern and southeastern regions of Kurdistan with 123 to 137 days, respectively, have the longest and shortest length of the frosted season. The longest growing season belongs to the eastern part of the province. The average growing season in this area is between 214 and 227 days. However, within this area, small sections that are lower in height have a longer growth period. On the other hand, the shortest growth period is in the western and northwestern mountains, averaging 116 to 129 days. Conclusion The results show that the three factors of altitude, latitude, and longitude can determine between 72 and 95% of the changes in different frost indicators. These three factors explain the 95, 90, 88, 80, and 72 percent changes in the length of the growth period, the occurrence of the first day of frost, the length of the frosted period, the frequency of frost, and the last day of frost, respectively. The Coefficient of determination is 95% for the first day of frost and 72% for the last day of frost. It seems that other factors besides the three mentioned factors play a role in changing the date of the last day of frost. Therefore, based on the studies of Noohi et al. in 2007, Noohi et al. 2009, and Alijani et al. in 2014, it can be inferred that the end frosts of the cold period can be more than the type of the advection frost. In other words, the synoptic factors can play a more important role in the occurrence of the last days of frost and its variability. But the spatial arrangement of different frost indices in Kurdistan province indicates a western to the eastern arrangement in the values of different frost indices. This means that with more movement from west to east, the number of frost days as well as the length of the frosted period decreases, and as a result, the growing season increases. In accordance with these changes, the occurrence of the first day and the last day of frost also arose with many delays between the eastern and western parts of the province. A comparison of the maps obtained from this algorithm showed that this method can provide more accurate details of the frost indicators compared to the zoning that used only stationary data (Mianabadi et al., 2009 and Ziaee et al. 2006).
Climatology
mahdi narangifard; mehran fatemi; abdolali kamaneh; mohammad sadegh talebi
Abstract
Introduction Recently, issues raised by changes in precipitation, especially problems brought about by floods and droughts, along with the environmental effects of diminished rainfall, have underscored the importance of precipitation studies at different temporal and spatial scales. Due to the pervasive ...
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Introduction Recently, issues raised by changes in precipitation, especially problems brought about by floods and droughts, along with the environmental effects of diminished rainfall, have underscored the importance of precipitation studies at different temporal and spatial scales. Due to the pervasive impact of precipitation parameter in various urban, industrial and agricultural fields with respect to water supply, the identification of fluctuations, changes and precipitation structure is of particular importance, especially in arid and semi-arid regions. The similarity feature in climatic variables allows the use of fractal geometry and analysis of temporal and spatial changes. Accordingly, the use of fractal geometry in predicting the behavior of many natural processes, including precipitation in different regions, has a special place. The goal of this study is to investigate the structure of different time periods of precipitation in Shiraz synoptic stations to explore changes and determine the spatial position of precipitation in the stability and instability period. Methodology In this study, daily precipitation data was received over a period of 58 years (1956-2013) from the Meteorological Organization of Fars Province to investigate the structure governing precipitation parameter. Then, statistical deficiencies were corrected by restructuring using difference ratio and linear regression. The methodology and algebraic logic of calculations in this study are such that in the first step, research parameters are arranged from minimum to maximum in an ascending order. Then, based on the triangular threshold coordinates(2Π), the minimum and maximum were extracted based on linear structures of the desired criteria and algebraic mathematical reference was conducted using Relation (1). Relation (1) F (x) = Then, in order to apply the fractal structure by applying the criterion for mathematical reference using Relation (2), the real structure of the desired meteorological parameters was obtained. Relation (2) Y = m2 × sin (1/m) Finally, by overlapping the output charts of the actual structures and the classical structure of the fractal (Figure 2) in the algebraic ranges of -0.4 to +0.4, the algebraic process of each climatic parameter was evaluated separately. Results and discussion In this study, based on the results, in addition to the daily analysis of the governing structure of precipitation over a 58-year period (1956-2012), which covered 21185 days, the governing structure along with the analysis of equilibrium dynamics of structures and its functions in three time periods (three 20-year periods) of different daily precipitation were also examined separately. The first period began in January 1, 1956 and lasted for 7065 days. The relevant calculations were performed on the data derived from the first period, which based on the findings of this study, precipitation in Shiraz''s synoptic stations do not follow the fractal logic in the first period by applying fractal algebraic structures, Also, in the second period, similar to the first one, the precipitation structure does not comply with a particular fractal logic. In other words, the logic governing precipitation parameter during the first and second periods changes from equilibrium to non-equilibrium. However, unlike the previous two periods, the fractal logic is followed in the third period. Conclusion The self-similarity feature in climatic variables allows the use of fractal dimension and analysis of temporal and spatial changes. Accordingly, the use of fractal geometry in predicting the behavior of many natural processes, including precipitation in different regions, has a special place. The goal of this study was to investigate the structure of different periods of precipitation in Shiraz synoptic station to identify changes and determine the spatial position of precipitation structure in the period of stability and instability. The behavior of meteorological parameters in various parts of the world is a function that never follows uniform algebraic structure. Therefore, the analysis of complex systems and changes in nonlinear climate parameters using chaotic, fractal and fuzzy concepts offers a suitable way to understand the equilibrium state and dynamic analyses of climate fractal changes. The results indicate the dynamic transition of this time period from non-equilibrium to equilibrium. Therefore, according to the three time periods, the equilibrium dynamics of the daily precipitation structure approaches fractal structure.
Climatology
Naser Mansourei Derakhshan; Bohlol Alijani; Majid Azadi; Mehry Akbary
Abstract
Introduction The weather fronts are known for their large vorticity, dense, moisture, and statical Stability gradients, and their longitudinal scale is one unit greater than their width. The width of the front is known as the baroclinical zone, in which the front lines have a very large ...
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Introduction The weather fronts are known for their large vorticity, dense, moisture, and statical Stability gradients, and their longitudinal scale is one unit greater than their width. The width of the front is known as the baroclinical zone, in which the front lines have a very large temperature gradient, which is determined by the angle between pressure and temperature lines. Position of a front is located in warm side of the extreme temperature gradient, inside the heat transfer zone and intensity of the front is determined by the size of the horizontal or quasi-horizontal temperature gradient.Even the numerous expert synopticians disagree with each other in the position of the fronts, their types and intensity, in the manual drawing method of the fronts. So their drawn fronts are very different While objective front is based on numerical methods and its purpose is to avoid applying people''s tastes in their manual method. The advantages of objective front metod in comparison with subjective front method are high speed front detection, the possibility of determining front frequeny, moving, and feedback of fronts with land side effects. So far, various methods have been developed for objective front method. They performed objective front method using numerical methods and the first and second derivatives of the temperature parameter on a regular grid points with a relatively low resolution of about 100 km. Inside the country, there has been no study about automatic and numerical front methods. On the other hand more than 90 percent of heavy rainfall in the tropics is associated with the fronts. Therefore, considering Iran''s location in the middle latitudes, it is very necessary to study and identify the fronts. So the climatological study of the manual front detectin is very time consuming, expensive and practically impossible. Therefore, in this research, the, automatic and numerical front detection have been discussed for the first time in the country. Methodology In this study, grid point data from the European Center for Medium-range Weather Forecasting (ECMWF) of type (ERA - Interim) is used with gaussian grid points. In this centre, different types of data are classified into different formats and in different time intervals and different grid resolution. In order to study of the fronts, isobaric level data with 6 hour intervals and resolution of 0.75 × 0.75 degrees with grib format is used. This grid resolution is set in a regular 61×61 matrix with a grid distance of 83 km. Different quantities can be used to select the appropriate parameter to detection of fronts such as temperature, humidity, wind direction and wind speed, vorticity, thickness and thickness changes ,and temperature is on of the most important of them. On the other hand, detection of the exact location of the extreme temperature gradient, which is accompanied by the effects of heating on the warm convergence belt in the warm side of the front leads to warm weather, can be identified only by using the equivalent potential temperature. Results and Discussion The main idea for identifying frontal areas is to use a temperature parameter in two-dimensional horizontal coordinates. The line representing the front in these areas is identified using a frontal identification function. In order to identify the front, the masking conditions are applied once or several times. In other words, in this equation, the horizontal gradients of the equivalent potential temperature are used, which should not be less than the value of the K-threshold value. >K . Several indicators are considered to identify the front. The first of them is that the front must be at a turning point in the curvature of the temperature lines which is along the temperature gradient. The second indicator is the location of the maximum values of temperature gradient,and the third criterion is the point where the second derivative of the temperature gradient is zero. Various experiments have shown that the smaller the temperature derivative of the front temperature parameter, the less error there will be (J. Jenkner, 2009). Thus, the Front Termal Parameter (TFP), invented by Renard & Clarke (1965), was used as the main method of frontal reconnaissance. TFP = In this equation, second derivative of the temperature parameter has been used, which has converted the temperature gradient, which is a vector quantity, to a scalar quantity. Conclusion Examination of the results of objective fronts showed that the detection of fronts near the ground due to the interaction between the boundary layer and the fronts is very erroneous and the fronts are practically indistinguishable. On the other hand, at higher levels, shallow fronts at numerical output are not detected. Therefore, the appropriate level for automatic identification of fronts in the study area, 700 hPa level was selected. Examining the results, it is inferred that cold and warm fronts are often found at the bottom of the ridge and above the ridge of the upper surfaces, and these fronts, during the formation stage, are often discontinuous and gradually evolve during the developmental stages. Strengthening the front will take a more integrated form. Studies have shown that cold fronts produce stronger frontogenesis than warm fronts. Also, the output of objective fronts showed that TFP is a good parameter for detecting the front in this region and with the results of previous studies such as Hewson (1998: 49), Jenkener et al. (2010: 9), they show a good match. The results of this study can be used in the discussion of climatology and forecasting of fronts and can be helpful in the discussion of flood management due to heavy rainfall on the front.
Climatology
Khalil Valizadeh Kamran; Soodabeh Namdari
Abstract
Introduction In recent years because of decrease of precipitation, use of water for agriculture, construction of hydraulic structures and etc, Urmia Lake surface area has been decreased. Considering the salinity of Urmia Lake and direction of wind, the costal and even further area of Urmia Lake is seriously ...
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Introduction In recent years because of decrease of precipitation, use of water for agriculture, construction of hydraulic structures and etc, Urmia Lake surface area has been decreased. Considering the salinity of Urmia Lake and direction of wind, the costal and even further area of Urmia Lake is seriously in danger of salt intrusion. Then knowledge of the spatial-temporal distribution of aerosol characteristics is critical for quantification of salt intrusion impacts. Aerosol optical depth (AOD) is a column-integrated measure of extinction coefficient, representing the attenuation of solar radiation by aerosol scattering and absorption. Satellite images of AOD are useful for studying dust storms owing to the large spatial nature of such plumes. Lack of an AERONET station makes studying dust storms difficult in this area. The present study was conducted to understand spatial AOD patterns and the variability and intensity of inter- and intra-annual MODIS AOD for the longest possible period of 14 years (2000–2015). Methodology In this study, monthly AODs from average MOD08 are used to investigate the spatial and temporal distribution of dust storms over Urmia lake for the period between 2000 and 2015. Monthly average MOD08 product files are available at spatial resolution of 1 degree by 1 degree (http://ladsweb.nascom.nasa.gov/data). This study focuses on AOD at 550 nm over land, as this is close to the peak of the solar spectrum and is, therefore, associated with major radiative effects (Papadimas et al. 2009). MODIS data are compared to AERONET data at the nearest station (Kuwait University) for the period between 2005 and 2014 (http://giovanni.gsfc.nasa.gov/aerostat/). The AERONET site shows better AOD correspondence with MODIS Terra (RMS = 0.028, R = 0.916) than with MODIS Aqua (RMS = 0.166, R = 0.646); therefore, hereafter AOD data are discussed from Terra. In this study, monthly mean aerosol optical depths (AODs) from MODIS are used to investigate the spatio-temporal distribution of aerosol in these affected areas (2000-2015). The monthly and annual mean AOD trends has been extracted. With the aim of displaying and analyzing the spatial distribution of particulate matter concentrations, the mean change map was extracted and each map was classified according to the standard deviation method. Using the standard deviation method, the amount of change in each of the pixels can be determined from the mean of the region. Results and discussion The changes in dust concentrations for shows that in June, July and April, there is the most similarity is between the trend of change in order in West Azerbaijan and East Azerbaijan. There are two provinces under study, and in February, November and December there is the most differences between the two provinces, which has declined sharply since 2009. Also, the trend of changes in all months shows that the slope of AOD changes has been increasing during the study period. Most monthly AOD fluctuations are seen in January, February and December during different years; It is worth noting that in these months, in terms of dust concentration, AOD also shows low values. The increasing trend of fine dust is much more pronounced at the end of the warm season and the beginning of the cold season (August, September, October and November). Most AOD values are observed in spring and early summer, ie in March, April, May, June and July. Until 2008, the amount of AOD in the southwestern part of the study area was high, indicating that fine dust observed in the southwestern part of the region could be carried by westerly winds from the deserts of neighboring countries during these years. From 2009 to 2014, the average amount of fine dust in Pixel of including Lake Urmieh, increased sharply over the entire region, which cannot be attributed to dust carried by western winds due to the AOD status in the west and southwest of the lake. Conclution In this study, annual and monthly averages were used to examine how dust changes in the last 16 years in the provinces of East Azerbaijan and West Azerbaijan, which are adjacent to Lake Urmia. One of the main objectives of this study was to monitor the oscillations of fine dust in the area of Lake Urmia and its adjacent areas to show the presence of salt dust in Lake Urmia, which has been the result of the drying up of large parts of the lake in recent years. The monthly and annual mean AOD trends show the increasing trend in AOD values. Then to show the spatial distribution during the period of study, mean annual maps for each year was extracted. Results show there is two seperated period in area of study for AOD spatial pattern. First during 2000 to 2009 there is higher AOD in south-western part of area and the existence of Urmia lake had caused reduction in AOD in western part of lake. Second period started from 2010 there is significant high AOD above Urmia lake. This fact shows the lake as a source of aerosols. In next step to show the spatial distribution of AOD changes during time, based on AOD value two years with high (2014) and low (2004) AOD was selected. The difference between these two years shows the most changes in area of study has occurred over Urmia lake and also around the lake. Based on the result of this study the increase of salty aerosols that originated from Urmai lake is one of major aspect of drought of the parts of lake and must be considered.
Geomorphology
Nayer Aghabeigi; Abazar Esmali Ouri; Raoof Mostafazadeh; mohammad Golshan
Abstract
Introduction Estimation of the rivers sediment load has high complexity due to effecting different parameters in this aspect. Regarding the power relationship between discharge data and suspended sediment load use of sediment rating curves is one of the most common methods for determining the sediment ...
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Introduction Estimation of the rivers sediment load has high complexity due to effecting different parameters in this aspect. Regarding the power relationship between discharge data and suspended sediment load use of sediment rating curves is one of the most common methods for determining the sediment yield in ungauged watersheds. Sediment condition shows the upstream characters and using the obtained data makes a relationship between erosion and sediment load. The different parameters such as climate, land use, data accuracy, and the applied methods have an effect on the sediment rating curve shape. Agriculture activities such as tillage in the direction of slope lead to accelerated erosion in the watersheds, especially in the Mediterranean area. These decades many studies assessing the effects of climate changes in the future period and it affects runoff. In this study, the main objective is to obtain sediment changes during the future decade (2011-2030) using the curve rating in sediment estimating. For this purpose, the IHACRES hydrologic model and the LARS_WG climate model were used. Material and Methode The IHACRES model for seven hydrometric stations was calibrated and validated. This model is rainfall and runoff erosion that require a little data for running including minimum and maximum temperature, rainfall, discharge and study are. This model defined as a lumped model and highly common in watersheds with scarce data. With running this model in all of the models the model parameters were calibrated. Also, the LARS_WG model was used for determining the weather changes that are occurring in the Samian watershed. This watershed has near to 4 thousand square kilometers that have many sub-watersheds. In this study, the watersheds in the west of the Samian watershed were selected for modeling. The average of rainfall in this area is between 220 and 457 mm, and the weather temperature changes in this region are high and that is between -32 to 34 C°. The results of LARS_WG showed the weather changes in each part of the hydrological model inputs that these changes were applied to the IHACRES model and the discharge flow rate was estimated for the future. On the other hand, using the observed discharge and sediment yield were calculated the sediment curve rate. By changes in flow discharge at the study stations, were calculated the suspended sediment discharges for the future period. results and discussion The results of the LARS_WG model showed that the amount of precipitation decreased to 3.68 percent and the minimum and the maximum temperature increased by 16.48 and 5.39 percent, respectively. Decreasing the input precipitation in most parts of the world particularly in Iran watersheds mentioned in many studies. One of the other the most important effect of climate change in this area is minimum and maximum temperature increase that leads to evapotranspiration increasing and soil moisture loss. The results of the IHACRES model showed that this model has a suitable capability for simulation runoff in the study area, therefore, it was used for estimating the future runoff regarding climate changes. The model output showed that during the next decades the average flow rate in the hydrometric stations will decrease by a total of 16 percent and the number of peak flood events will increase, that the highest increase between the study watersheds observed in the Yamchi hydrometric station with a mean of 2.09 m3s-1 and 16 peak events with over 6 m3s-1. Using the obtained results of the climatic model, hydrological model and the sediment rating curve the suspend sediment changes were estimated for the future period. The result shows that these climatic changes will lead to a 47 percent reduction in the average suspended sediment load at study stations. Conclusion The consequences of climate change have a significant effect on water resources quality and quantity. The aims of this study were to calculate the weather changes and it's ruling on discharge and sediment yield changed. the results of this study indicate the effect of climate change on the Ardabil province watersheds is remarkable. Considering the environmental impacts of climate change and dependence on human life on the environment it is necessary to implement an appropriate approach for decent management in Watersheds. Keywords: Rating curve, climate change, LARS-WG, discharge, IHACRES.
Climatology
Ali Mohammad khorshiddoust; Kaveh Mohammadpour; Seyed Asaad Hosseini
Abstract
Introduction Prediction of hospital admissions related to climatic parameters is discussed matters that in recent decades in result from climate change, urbanization and air pollution has triggered widespread in many societies. Fluctuations in climatic parameters, in turn, can have a significant impact ...
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Introduction Prediction of hospital admissions related to climatic parameters is discussed matters that in recent decades in result from climate change, urbanization and air pollution has triggered widespread in many societies. Fluctuations in climatic parameters, in turn, can have a significant impact on mortality and mortality, and the use of predictive models can be used to identify fluctuations in climatic parameters affecting disease and their prevalence and planning and Compatibility with the environment to be effective. Methodology Using of predictive models can be consider as an effective tool in managing and controlling the diseases, reducing mortality and planning. Recent study used from Artificial Neural Networks and Logistic Regression models as an effective tool in the prediction of nonlinear processes to predict the rate of asthma admissions related to Climatic parameters in Sanandaj/Sine city. Used data during period of 8-years (2001-2008) collected from synoptic station and Toheid and Beasat hospitals in the Sanandaj/Sine city. Then, the climatic parameters and rate of asthma admissions considered as an input and output data of models, respectively. Result and Discussion The results of the output of two nonlinear models of artificial neural network and Logit in examining the effect of climatic parameters on the number of the asthma patients in Sanandaj/Sine showed that the monthly average parameters with high coefficient of determination (R2=0.98) of temperature (average, minimum, maximum) and QFE pressure in the artificial neural network model and The monthly average minimum temperature, QFF pressure and wind speed (in Knot) in the Logit model have had the greatest impact on the rate of asthma admissions in the city. As the wind speed in the Logit model is more effective than other climatic parameters, that it is clear with the logarithmic superiority (-0.977) and the Wald coefficient (85.616). In general, air pressure, temperature and wind speed are the most effective climatic parameters on the number of asthma patients visiting the hospital. Therefore, depending on the accuracy of the models, the above argument means that among the parameters examined, the elements are more important than other parameters in the city. As the climatic elements have a more effective role in the admission patients to the hospital, and their fluctuations will be more significant in patients' fluctuations. The effects of environmental parameters (climate and pollutants) on diseases have previously been investigated as well, so that the results of previous logistic regression have display a increase respiratory disease, vulnerability of children to asthma and an increase in allergies; In the present study, the results of Logit model (69.5%) also indicate that decrease in the average minimum temperature lead to a decrease in the number of the asthma patients, it means that the rate of asthma is more less in temperatures close to zero or higher and vice versa, the admission more higher in the colder temperature (below zero); in the other words, the more balanced the temperature has the lower the rate, and in the colder the ambient temperature has the highest the number of asthma patients. Thus, comparison the present results and previous studies show that admissions change depending on climate, geographic position and the fluctuation of the elements and then the specific geographical location and the different climatic types of a region will play a decisive role in the number of asthma visitors to hospital. Conclusion The results indicated that Artificial Neural Network model predicted the asthma admissions related to monthly minimum, maximum and average temperatures with considerable accuracy, so that the correlation between actual and predicted data is significant with 0.01 coefficient and 0.99 confidence. Also, Input parameters in the Logit method shows that the rate of asthma admissions affected by parameters of average minimum temperature, average pressure QFF and average wind speed (in knot). In other words, the logarithmic ratio of each of cited parameters is significant with β-coefficients (-0.517), (-0.734) and (-0.977), respectively, that throughout of studied parameters is wind element of effective in asthma admissions then others to the hospital. In general, Artificial Neural Network model showed more sufficiency and accuracy than Logit model. As a result, both Logistic Regression and the Artificial Neural Network methods show that climatic parameters have a greater than 50% effect on the number of asthma patients referred to the hospital (the accuracy models: 69.5 and 98, respectively). In the Artificial Neural Network model, the most accurate possible result shows the more effective role of climatic parameters of temperature and air pressure on the asthma patients. Also, filtering the parameters examined at the output of the Logistic model showed the most possible coefficients for minimum temperature, QFF air pressure and wind speed (knot), among which wind speed was the most important element. Finally, the accuracy of the models showed that the Artificial Neural Network model has a higher accuracy depending on the coefficient of determination and highest correlation. Thus, Artificial Neural Network and Logit as nonlinear methods could well predict the relationship between climatic parameters and the number of the asthma patients. Also, according to the appropriate selection of input parameters and determination of different structures in the neural network is possible to design different models with the highest efficiency and can be considered as an effective and powerful tool in estimating similar studies. Introduction Prediction of hospital admissions related to climatic parameters is discussed matters that in recent decades in result from climate change, urbanization and air pollution has triggered widespread in many societies. Fluctuations in climatic parameters, in turn, can have a significant impact on mortality and mortality, and the use of predictive models can be used to identify fluctuations in climatic parameters affecting disease and their prevalence and planning and Compatibility with the environment to be effective. Methodology Using of predictive models can be consider as an effective tool in managing and controlling the diseases, reducing mortality and planning. Recent study used from Artificial Neural Networks and Logistic Regression modelsasan effective toolinthe prediction ofnonlinearprocessesto predict the rate of asthma admissions related to Climatic parameters in Sanandaj/Sine city. Used data during period of 8-years (2001-2008) collected from synoptic station and Toheid and Beasat hospitals in the Sanandaj/Sine city. Then, the climatic parameters and rate of asthma admissions considered as an input and output data of models, respectively. Result and Discussion The results of the output of two nonlinear models of artificial neural network and Logit in examining the effect of climatic parameters on the number of the asthma patients in Sanandaj/Sine showed that the monthly average parameters with high coefficient of determination (R2=0.98) of temperature (average, minimum, maximum) and QFE pressure in the artificial neural network model and The monthly average minimum temperature, QFF pressure and wind speed (in Knot) in the Logit model have had the greatest impact on the rate of asthma admissions in the city. As the wind speed in the Logit model is more effective than other climatic parameters, that it is clear with the logarithmic superiority (-0.977) and the Wald coefficient (85.616). In general, air pressure, temperature and wind speed are the most effective climatic parameters on the number of asthma patients visiting the hospital. Therefore, depending on the accuracy of the models, the above argument means that among the parameters examined, the elements are more important than other parameters in the city. As the climatic elements have a more effective role in the admission patients to the hospital, and their fluctuations will be more significant in patients' fluctuations. The effects of environmental parameters (climate and pollutants) on diseases have previously been investigated as well, so that the results of previous logistic regression have display a increase respiratory disease, vulnerability of children to asthma and an increase in allergies; In the present study, the results of Logit model (69.5%) also indicate that decrease in the average minimum temperature lead to a decrease in the number of the asthma patients, it means that the rate of asthma is more less in temperatures close to zero or higher and vice versa, the admission more higher in the colder temperature (below zero); in the other words, the more balanced the temperature has the lower the rate, and in the colder the ambient temperature has the highest the number of asthma patients. Thus, comparison the present results and previous studies show that admissions change depending on climate, geographic position and the fluctuationof the elements and then the specific geographical location and the different climatic types of a region will play a decisive role in the number of asthma visitors to hospital. Conclusion The results indicated that Artificial Neural Network model predicted the asthma admissions related to monthly minimum, maximum and average temperatures with considerable accuracy, so that the correlation between actual and predicted data is significant with 0.01coefficient and0.99 confidence.Also, Input parameters in the Logit method shows that the rate of asthma admissions affected by parameters of average minimum temperature, average pressure QFF and average wind speed (in knot). In other words, the logarithmicratio ofeach of citedparametersissignificant with β-coefficients (-0.517), (-0.734)and(-0.977), respectively, thatthroughoutofstudied parametersis windelement of effective in asthma admissionsthen others to thehospital. In general, ArtificialNeural Networkmodelshowed more sufficiencyandaccuracy than Logitmodel. As a result, both Logistic Regression and the Artificial Neural Network methods show that climatic parameters have a greater than 50% effect on the number of asthma patients referred to the hospital (the accuracy models: 69.5 and 98, respectively). In the Artificial Neural Network model, the most accurate possible result shows the more effective role of climatic parameters of temperature and air pressure on the asthma patients. Also, filtering the parameters examined at the output of the Logistic model showed the most possible coefficients for minimum temperature, QFF air pressure and wind speed (knot), among which wind speed was the most important element. Finally, the accuracy of the models showed that the Artificial Neural Network model has a higher accuracy depending on the coefficient of determination and highest correlation. Thus, Artificial Neural Network and Logit as nonlinear methods could well predict the relationship between climatic parameters and the number of the asthma patients. Also, according to the appropriate selection of input parameters and determination of different structures in the neural network is possible to design different models with the highest efficiency and can be considered as an effective and powerful tool in estimating similar studies.
Climatology
Majid Rezaei Banafsheh; fatemah jafarishandi; Fereshteh Hossien alipour Jazi
Abstract
Introduction In this study, to analyze the effect blocking system on the precipitation during 1379 Sample rain, the weather maps of mean sea level pressure, geopotential height at 500 hpa level, wind components, moisture flux convergence and were analyzed. The data of daily precipitation were analyzed ...
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Introduction In this study, to analyze the effect blocking system on the precipitation during 1379 Sample rain, the weather maps of mean sea level pressure, geopotential height at 500 hpa level, wind components, moisture flux convergence and were analyzed. The data of daily precipitation were analyzed for meteorological stations by using Environmental approachto circulation during 1951 to 2013.The results suggest that three patterns have been effective in a rain storm and the establishment of Scutoff low in the Wast North West Iran and its associated trough displacement and ground accompaniment, which have provided the conditions for the creation of heavy rainfall. Because heavy rainfall is a type of atmospheric anomaly, many researchers are looking at how it occurs in abnormal weather patterns, including blocking patterns and other unusual synoptic patterns. Systems that are cut from the main west turn are called blocking systems (Habibi, 2006: 70). Researchers who have studied blocking systems such as Silman (2008) using the atmospheric-ocean output model, Kumar et al. (2008) using the air forecasting model, Timevios et al. (2010) using the Self Orgnizing Map (SOM), Caspar and Muller (2010) used the clustering method of hierarchy and Hang et al. and Yarahmadi and Marijanji (2011) by studying the low pressure system on the earth's surface, the atmosphere of the mid-atmosphere and the rise of cold weather And Gavidel (2014) have studied blocking system with the occurrence of blocking at 500, 600 and 700 hectopascal levels. Methodology In this study, High-level atmospheric data for rainfall analysis of days that have been rainy for more than 1 day include altitude geopolitical data of 500 HPL (meter potential), Uwind and Vwind (meters per second) and special humidity (grams per kilogram). These data are from 00:00, 06:00, 12:00 and 18:00 Greenwich Mean Time in the range of 0 to 80 degrees north and 0 to 120 degrees east with a spatial resolution of 2.5 × 2.5 degrees. It has been extracted from a database (NCEP / NCAR) affiliated with the United States National Oceanic and Atmospheric Administration. First in the form of an environmental approach to circulation, Rainfall of more than one day in the spring during 62 years of statistics, which is 1379 days, was extracted. From these 1379 rainy days, based on the base index of 99th percentile, precipitation of more than 25.88 mm was selected. Therefore, 58 days of precipitation became the basis for the study of heavy spring rains. Because the purpose of the work is to check the blocking, the period of precipitation should be more than one day to determine the cause of heavy precipitation based on blocking or other systems. Then, using cluster analysis, the clustering of these 58 rainy days was studied. The results showed that three pressure patterns are effective in creating rainfall in Tabriz. For each of the patterns, a representative day with a correlation threshold of 95% was calculated and analyzed. Results and discussion At the time of pressure pattern 1, the Siberian high-pressure range stretched from 45 to 55 degrees north latitude to the west to the northern latitudes of Iran, and with low pressure on Turkey, provided thermal gradient. At the pressure pattern 2, a strong high-pressure nucleus with about 1032 HPL was formed in northern Mongolia. The tabs on this core, along with the high-pressure tabs of Siberia, have created extremely stressful conditions at the site of the low-pressure collision on northwestern Iran and Turkey. At the time of the establishment of the pressure pattern 3, tabs of the high-pressure system of the Scandinavian islands were drawn from the Black Sea to northwestern Iran. On the other hand, the whole of Iran is covered by the low pressure spread by Saudi Arabia. These conditions have led to an increase in the temperature and the provision of fronts and instability in Tabriz. In this way, the heavy rainfall that can be seen in the depths of the heart of this instability can be justified. Conclusion The results of synoptic analysis of pressure patterns related to blocking effective on the occurrence of heavy rainfall in Tabriz area indicate the formation of blocking phenomenon of high pressure type on the region. This system stops the movement of air circulation patterns, during which the patterns governing the atmosphere remain in place for several days. In the face of this system, the waves of the western winds are divided into two branches, north and south. This allows the waves to travel further north or south.
Urban Planning
Atefeh Shahmohammadi; Ali Bayat; Saeed Mashhadizadeh Maleki
Abstract
Introduction Today, the unfavorable weather conditions are one of the critical problems in the world's major cities, which have many harms to humans and the environment. Nitrogen monoxide and nitrogen dioxide are important air pollutants. Nitrogen dioxide is a reddish-brown gas with a pungent odor. ...
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Introduction Today, the unfavorable weather conditions are one of the critical problems in the world's major cities, which have many harms to humans and the environment. Nitrogen monoxide and nitrogen dioxide are important air pollutants. Nitrogen dioxide is a reddish-brown gas with a pungent odor. The most important human resources producing this pollutant are car exhaust and fixed sources such as fossil fuels, power plants, incinerators, and home heating appliances. In addition to human resources, nitrogen oxides are also produced by bacteria, volcanoes, and lightning. The city of Tabriz is one of the metropolises of Iran, and the increase in the population of the city, motor vehicles, consumption of fossil fuels, industrial activities, and improper use of heating devices and the existence of industrial factories has increased energy consumption in this city and many problems. It has created an environment for the residents of this city. The purpose of this paper is to study the trend of nitrogen dioxide as an indicator of air pollution from OMI data using linear fit after eliminating significant rotation periods on the time series of the average monthly nitrogen dioxide for the city of Tabriz. Methodology In this study, the nitrogen dioxide data measured by the OMI satellite sensor and the wind data, the surface temperature and the horizontal visibility measured with the synoptic station during the years 2004 to 2016, contaminated with airborne nitrogen dioxide emissions in Tabriz city is being investigated. The seasonal mean and nitrogen dioxide, temperature, wind, and horizontal visibility, as well as the correlation between nitrogen dioxide and meteorological data, have been investigated to better understand the changes in air pollution. To understand the properties and behavior of the functions, they can be examined in frequency space. Least square spectral analysis can be used to investigate non-distant time series. Statistical tests can also be performed until the periodic intervals obtained from the spectral analysis are statistically validated. After the formation of the time series, the average monthly nitrogen dioxide level between the 2004 to 2016 intervals was observed using spectral analysis of least squares of periods of four, six, and twelve months, which were also statistically significant. To calculate the nitrogen dioxide trend, significant components are eliminated from the time series. After eliminating the significant components of the four, six, and twelve months of the nitrogen dioxide time series, the trend is calculated using linear fit on the remaining time series. Results and discussion The results showed that the highest amount of nitrogen dioxide occurs in cold season and the lowest amount in hot seasons. The average nitrogen dioxide content in the spring, summer, autumn and winter seasons was equal to 2.13, 1.90 ×, 3.88 × and 5.36 × molecules per cm2 and its mean value was calculated at 2.84 × molecules per centimeter square. Also, the highest amount of standard deviation of nitrogen dioxide occurs in winter, 10.4 and its lowest value in summer, 0.97 The study of temporal, wind, and horizontal visibility of Tabriz city for the measurement period 2004 to 2016 shows that nitrogen dioxide and temperature have a relationship. So that nitrogen dioxide has the highest amount in the early and the late months of the year when it is cold, and vice versa. 96 percent of the winds of the city of Tabriz have a speed of less than 0.5 meters per second, so called quiet winds and the prevailing winds of the eastern and northeastern cities. The correlation coefficient of nitrogen dioxide with wind and temperature was -0.49 and -0.32, respectively, indicating a greater significance of wind in the variation of this pollutant. One of the simplest ways to check the air quality is horizontal visibility. The correlation coefficient of nitrogen dioxide with horizontal visibility for Tabriz city is -0.09 and its value has not been significantly different during the year. The amount of nitrogen dioxide in each year for Tabriz was 1.05 × molecules per cm2. Conclusion Paying attention to the quality of life and environmental issues in the city of Tabriz is very important due to population growth and increasing urban life. Air pollution caused by nitrogen dioxide in the cold seasons of the year was mostly due to temperature inversion. As a result, what plays a significant role in air pollution in this city is the increase in urbanization, the development of factories, and the excessive use of fossil fuels, power plants, and motor vehicles. Therefore, adequate measures must be taken to reduce air pollution in order to maintain the health of citizens and the environment. One of the factors reducing air pollution is green space, and the city of Tabriz does not have a great green space, so the lack of green space in this area is strongly felt and is very small compared to international standards.
Climatology
Mohammad Hosein Gholizadeh; Samira Hamidi
Abstract
Introduction The consequences of climate change, changes in precipitation characters, including the amount, time and it’s duration are expected. Considering that the rain provides the water resources on the planet, change in regime, amount and duration of rainfall, caused a disturbance in the ecosystem ...
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Introduction The consequences of climate change, changes in precipitation characters, including the amount, time and it’s duration are expected. Considering that the rain provides the water resources on the planet, change in regime, amount and duration of rainfall, caused a disturbance in the ecosystem of the Earth. It also affects the environmental conditions. Kurdistan province has an agricultural economy, thus variation in the rainfall duration can affect agricultural activity and other activities. To achieve success in the environmental management planning and efficient use of water resources over an area, it is essential to have information about rainfall variation. An important parameter of atmospher is precipitation.It has a lot of changes over the time and space. It is a basic element in the formation of the activities and prospects of the environment. Several studies have done by researchers on the properties of precipitation in the different regions of the world and also in Iran. In general, precipitation showed a negative trend in many regions (Gorgio,2002: 675). For example, an assessment of summer rainfall in eastern China showed a positive and a negative trend in the north (Gemmer et al, 2004: 39; Gong et al, 2004: 771).Annual rainfall has decreased in southern parts of Italy and the decrease in winter precipitation was larger (Marco et al, 2004: 907). An increase in summer rainfall, especially, in June and July has been reported in the Yangtze River basin (Tong et al, 2007: 1016). A decrease in winter rainfall and an increas for other seasons has been showed in Turkey (Kahya and Partal, 2007: 43). Evaluation of maximum daily rainfall at the global scale showed an increasing trend in rainfall (Sethwestra et al. 2013: 3904). Negative anomalies of precipitation was reported for the most stations in southern west Ethiopia (Girma et al. 2016: 3037). Based on Iran's annual rainfall, positive and negative trends in annual rainfall have been showed (Asgari and Rahimzadeh, 2006: 67). A decrease in rainfall, especially in the decade of 1995-2005 revealed in Iran using annual rainfall (Asakereh and Razmi,2012: 159). Assessment of changes in seasonal patterns of rainfall in Hamedan, showed that the beginning of the rain tend to the summer and the end of winter (Movahedi et al.,2013: 23). The results of precipitation extreme indices on Iran showed a positive trend in the west and the south west and a negative trend in the north (Masoodian and Darand, 2013: 239). Methodology For this study, the daily precipitation obseravtions obtained from synoptic stations in Kurdistan province during 01.01.1989 to 31.12.2014 were anlayzed. A database with dimensions of 9526 * 8 was created. The time was set on rows (9526 days) and the rainfall was set on columns. Homogeneous and heterogeneous monthly rainfall data were assessed by apply cumulative deviations test and Vercelli maximum of likness. Mann-Kendall approach was implemented to extraxt the trend at the significant level of 90%, 95%, and 99 %. The significant differences in the mean of time series data before and after a mutation year by Mann-Whitney test were evaluated. The statistical calculations were done in the Matlab software. Results and Discussion The results showed that during the study period, duration of rainfall for autumn, winter and spring, in most of the stations, has been reduced. The results indicated that the rainfall duration for summer showes an increases in rainfall.Which is in line with the result of many previous studies.The reduction in the rainfall in the rainy season and an increase in rainfall in summer were obsorved. As a result the duration rainfall also has been changed. Annual rainfall has decreased in southern Italy and decrease in precipitation in winter is more (Marco et al, 2004: 907). Movahedi et al. 2013, By studying the seasonal rainfall in Hamadan, They found that the rainfall began to ward the winter and their end to the summer have changed. Conclusion Evaluation of duration time series of rainfall over different months of the year showed that in the rainy months of autumn, winter and spring rainfall duration has decreased. For example, Baneh station showed a decline of 0.3 day in December, and Marivan showed a decline of 0.6 day in January. The average rate of decline in rainfall duration in March for the Qorveh station was 0.4 day per decade. In addition, a decline in spring rainfall duration was observed as well. Bijar station showed a decline of 0.2 day in May. However the rainfall duration in summer showed an increase. For example, Zarinah station obtained an increase of 0.2 day per decade in August.
Climatology
sakineh kadkhodaei; Saeed Jahanbakhsh asl,; Khalil Valizadeh Kamran
Abstract
Introuduction Snow reserves of mountain areas considered as one of the most important water resources of country which accurately recognition of quantity of these resources are essential due to the increasing value of freshwater and optimal utilization of resources. Sabalan mountain are one of the important ...
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Introuduction Snow reserves of mountain areas considered as one of the most important water resources of country which accurately recognition of quantity of these resources are essential due to the increasing value of freshwater and optimal utilization of resources. Sabalan mountain are one of the important basins of country that the water from melting snow which has fallen in winter, provide water for agriculture and surrounding areas drinking in spring and summer. In this study for simulations runoff from snowmelt in the Sahzab catchment, (of sub-basin in the southern part of Sabalan) from mod 10a2 product and changes in snow cover of 2010-2011, using SRM model(based on degree-day method), has conducted. Results suggest during the statistical period, the greatest and lowest amounts of snow coverage are for February and may, respectively. Methodology The Snowmelt Runoff Model (SRM) as the most frequently used model in model in prognosticating and simulating runoff in mountainous basins using snow covered areas as an input, was employed in current study to simulate the runoff produced from snowmelt. The S factor (snow cover area) was extracted using 8 day images of MODIS sensor (combining bands number 6 and 4), NDSI index (with the necessary thresholds) ENVI and GIS software. In order to achieve the desired objectives, ground data such as temperature , rainfall and debit were also used. Results and discussion Evaluation of SRM model using correlation coefficient and volume subtracting indicator are 81 and 2/3 percent, respectively. R-value indicator acceptability depends on the quality of data and may not be acceptable even by having enough data of 85% value but in a catchment with inappropriate and low data, lower value also is acceptable. With respect to shortage of meteorological and terrestrial data in Sahzab catchment, the SRM results of this study showed acceptable simulations for runoff simulation that was caused by snow melting in sahzab catchment. Conclusion Using of hydrological models and satellite images combined with powerful ground-based data can be used as a tool for planning and management of water resources, particularly in the area where snow melting is one of the factors leading to runoff. If studies on snowcovered area, snowmelt and its effects are considered on small scale such as riverside tributaries extraction of snow cover maps for each of the catchment basins, careful planning can be done for each region which will be in line with sustainable development.
Climatology
Atefeh Hoseini Sadr; Gholam Hasan Mohammadi; Firooz Abdoul Alizade; Vaheid Khjaste Golamei
Volume 23, Issue 70 , March 2020, , Pages 79-100
Abstract
Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were ...
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Heavy rainfall occurrence on April 14th, 2017 which followed by flood in Azarshahr and Ajabshir regions caused 48 deaths at East Azerbaijan province. Detecting synoptic mechanisms for such event was our main motivation for this study. In this regard, observational, upper atmospheric and SkewT data were used. First, spatial distribution of precipitation in the study area was plotted. Then, Geo-potential height, vorticity and omega, specific humidity, moisture transition, jet stream for upper level and Huff-Muller chart were analyzed for different atmosphere layers. Finally, some atmospheric stability indexes were surveyed by using SkewT charts. Results showed that, highest rainfall was occurred as a rain corridor between southwest of West Azerbaijan province and middle regions of Urmia Lake to the central regions of East Azerbaijan Province with 30 to 57 mm range. Synoptic maps showed that in this day simultaneous expansion of the ascending area of Mediterranean trough in mid atmospheric layers and the core of polar Jet stream in upper levels provided favorable conditions for unstable atmosphere on the northwest of Iran, so that the amount of omega was less than -0.3 Pascal per second. Specific humidity maps indicate that, at the same time a significant moisture flux has flown from the Red Sea to the northwest of Iran. Therefore, the rapid conversion of atmospheric moisture into the rain in the ascending area of Mediterranean trough was the main cause of the heavy rainfall occurring on this day. This issue was proved by convergence moisture flux map and the Hoff-Müller graph. SkewT charts and instability indexes of Tabriz station also confirmed high amount of moisture and favourable ascending conditions in the atmosphere on April 14th
Climatology
mehdi asadi; Ali Mohammad Khorshiddoust
Volume 23, Issue 70 , March 2020, , Pages 101-122
Abstract
Limited fossil energy source and increase of energy use is always pushed man to replace the energy source. In this case the winds have always had a special place in the new generation of energy sources. East Azarbaijan province because of the topographical and relativity situation is one of the best ...
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Limited fossil energy source and increase of energy use is always pushed man to replace the energy source. In this case the winds have always had a special place in the new generation of energy sources. East Azarbaijan province because of the topographical and relativity situation is one of the best places for building a wind farm. therefore this research have been done to find out the best places for building wind farms in East Azarbaijan province, to find this places different criteria and sub criteria have been used. Given the importance of information fusion, analytic hierarchy process (AHP) were selected for weighting the layers and were implemented by the help of Expert choice software. For special analyses and overlapping of layers the Arc GIS program have been used and after the analysis of information, according to the capacity of building wind farms, province of East Azarbaijan have been divided to four parts, great, good, normal, weak. At last, final conclusions represent that Geographic Information System as a Supportive Decision making system can be practical both in preparing of data and designing the priorities and expert's ideas dealing with different factors and also help the designers to select the proper location to found the wind farms. In this research,15 regions have been determined, considering priority of, overlay, limitation of land and places, survey of priority area, climate condition and personal observation have been determined that in sequence this places are Tabriz, Sahand, Osko, Azarshahr, Bostanabad, Shabestar, Jolfa, Haris, Miyane, Bonab, Marageh, Sarab, Ahar, Charayomagh and Hashtrod.
