Climatology
asadollah khoorani; zahra jamali
Abstract
The aim of this paper is assessment and comparison of potential impacts of climate change on drought indices in an arid and a semiarid station. For this purpose, daily data of minimum and maximum temperature, sunshine and precipitation are used. This data were downscaled statistically by using ...
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The aim of this paper is assessment and comparison of potential impacts of climate change on drought indices in an arid and a semiarid station. For this purpose, daily data of minimum and maximum temperature, sunshine and precipitation are used. This data were downscaled statistically by using LARS-WG model based on A2, B1 and A1B scenarios. These climatic parameters are projected for 2011-2040, and RDI index was extracted for both observed (1961-1990) and projected data from HADCM3 model. The research outcomes show drought severity has increased under each scenario in both stations, except for Shahrekord under B1 scenario. For Bandarabbbas station, percent of droughts are about 6.7, 10 and 10 under A1B, A2 and B1 scenarios respectively. This parameter is 6.7 and 3.3 percent under A1B and A2 in Shahrekord station and the number (percent) of droughts will decrease about %10 under B1 scenario in this station.
Climatology
Ali Mohammad Khorshiddoust; Ali akbar Rasouli; Ali Slajegheh; Mojtaba Nassaji Zavareh
Abstract
One of the important arguments in variability and climate change assessment is the accuracy of climatic time series analysis. Therefore time series to be used should be homogeneous. Annual and seasonal maximum and minimum temperatures of 5 synoptic stations that contain long time series have been assessed ...
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One of the important arguments in variability and climate change assessment is the accuracy of climatic time series analysis. Therefore time series to be used should be homogeneous. Annual and seasonal maximum and minimum temperatures of 5 synoptic stations that contain long time series have been assessed in this study. For so doing, we utilized direct and indirect methods. We used metadata through indirect method and absolute and relative standard normal homogeneity test through direct routine. Results showed inhomogeneity which was identified by statistical methods corresponding to metadata. Relative standard normal homogeneity test is more suitable than absolute standard normal homogeneity test in this concern. Assessment of homogeneity between annual and seasonal minimum and maximum temperatures indicates that the parameter of minimum temperature has more inhomogeneity in the data. Comparison of homogeneity results between temperature of warm and cold season reveals that the temperature is more stable during relocation and other changes in cold season than in warm season. Relocation of many stations was not proved to be the cause of inhomogeneity in annual and seasonal maximum temperatures.
Climatology
Bohlul Alijani; Ali Bayat; Mehdi Doostkamian; yadollah Balyani
Abstract
Precipitation is one of the most essential and variable climate components whose understanding has long been a concern for climatologists. The main objective of the current paper is to investigate and analyze the precipitation cycles in Iran. In order to realize this objective, the annual precipitation ...
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Precipitation is one of the most essential and variable climate components whose understanding has long been a concern for climatologists. The main objective of the current paper is to investigate and analyze the precipitation cycles in Iran. In order to realize this objective, the annual precipitation data of isometric station of Iran were extracted. These data have been collected by the country’s meteorological organization since the establishment of the station until 2008 which adds up to more than 40 years of statistics. Then, in order to investigate and analyze the precipitation cycles, spectral analysis (co-structural analysis) was utilized. Regarding the calculations, the programming utilities of Matlab were used and the Surfer software application was exploited for drawing operations. The results obtained from analyzing the cycles show that there are significant 2 to 3 year cycles, 3 to 5-year cycles, 2 to 6 year cycles and sometimes 11 or more- year cycles governing Iran’s precipitation patterns. Hence, in east and southeast of Iran, 3 to 5-year cycles are prevailing and in west and northwest 2 to 3-year cycles are dominant and finally in north east 2 to 6-year cycles are customary. The most numerous and the most variable cycles happen in south and south east, mainly due to the mountainous regions of Zagros as well as the proximity to Persian Gulf. The north western regions, much like the southwestern regions, indicate variable cycles due to the mammoth mountains of Sabalan and Sahand. Moreover, the presence of those cycles which have a return period equal to the statistical period has been seen in various parts of Iran, which indicates a precipitation trend in this country.
Climatology
Hasan Zolfagari; Bahman Farhadi; Hamid Rahimi
Volume 20, Issue 56 , August 2016, , Pages 89-105
Abstract
The evaluation of environmental conditions in particular climatic conditions of crops such as soybean that have a great economic importance for the country. In this regard, climate regions, with a minimum requirement of soybean cultivation were identified. By choosing a 20-year period from 1989 to 2008 ...
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The evaluation of environmental conditions in particular climatic conditions of crops such as soybean that have a great economic importance for the country. In this regard, climate regions, with a minimum requirement of soybean cultivation were identified. By choosing a 20-year period from 1989 to 2008 and precipitation map of Iran on the basis of all available stations over 20 years of daily data completed, three regions with annual rainfall of over 500 mm in the North, West and South West were then determined. To increase precision, creating a virtual stations on the basis of daily maximum and minimum temperatures, areas outside of the internal parts were removed and each of the relevant area, was approved to determine the ultimate potential. Using CGMS software, the minimum temperature, maximum vapor pressure, sunshine hours and wind were estimated for rainfall estimation from Completely Regularized Spline (CRS) method, and Spline Regularize (SR) method was used to estimate relative humidity. In the next phase, the mean rate of deficit in soybean yield in dry land conditions was determined using the CROPWAT. Then, three valuable layers of precipitation, relative humidity and maximum temperature were explained by the use of AHP to determine the weight of each layer which was overlapped. The results showed that in the West and South West regions, with the percentage deficit crop yield of over 50%, conditions are low to moderate but the western half of the country's northern region can be considered suitable for soybean cultivation. Calculations showed that the deficit efficiency of the crop in this region, was less than 10 percent and thus has good potential for rain-fed soybean cultivation. It also became clear that to start rain-fed soybean cultivation in all regions, the month of Ordibehesht was more suitable than other months.
Climatology
Majied Rezaee Banafshe; Fateme Jaafari Shendi; Fereshte Hosseinalipour Ghazi; Majied Alimohammadi
Abstract
In this study, frequency and location of Moisture Flux Convergence (MFC) related to heavy rainfall have been analyzed using environmental to circulation approach. Based on the threshold of upper 99 percent, we selected 106 days of the super and overall heavy rainfall from IRIMO data base. MFC’s ...
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In this study, frequency and location of Moisture Flux Convergence (MFC) related to heavy rainfall have been analyzed using environmental to circulation approach. Based on the threshold of upper 99 percent, we selected 106 days of the super and overall heavy rainfall from IRIMO data base. MFC’s frequency and their locations have been detected from 00 to 1200 E and 00 to 800 N in the five levels (1000, 925, 850, 700, 600 and 500 HPa level) at 00:00, 06:00, 12:00 and 18:00 UTC. Analysis of MFC indicated that among upper levels, frequency of MFC in 850 hPa, due to high frequency is very important
Climatology
MohammadHoseein Rezaei Moghaddam; Khalil Valizadeh Kamran; Mehdi Belvasi; Hoseein KheiriAstiyar; Sayad Asghari Saraskanroud
Volume 20, Issue 56 , August 2016, , Pages 127-148
Abstract
One of the most important procedures in the water sources studies is the estimation of the local distribution of precipitation in different time scales. The study of precipitation is a basic element in the water balance studies and is an important factor in the natural sources programs of each country. ...
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One of the most important procedures in the water sources studies is the estimation of the local distribution of precipitation in different time scales. The study of precipitation is a basic element in the water balance studies and is an important factor in the natural sources programs of each country. Also, because of the rain-evaluation stations deficiency and their discreteness, it is necessary to use a special model. Besides the interpolation of precipitation amounts of stations, this model should interpolate topography, moisture and the slope direction of precipitation. In this work, at first, some data were gathered, in one year. These data were connected with the precipitation and moisture of 9 synoptic stations and 31 rainevaluation stations. These stations were located in the Lorestan province. Second, using the least square method and with the help of Maple software, the relations between precipitation and moisture was extracted. Third, by using the Python programming language, these relations were linked into the GIS. Finally, by so doing, the digital precipitation modal was achieved. The results obtained from the digital precipitation model show that, the precipitation amounts are different from the measured data in the stations, from 0.02 to 11.6 mm. Also, to investigate the efficiency of the considered model, the data obtained from this model were compared with the precipitation data achieved from TRMM radar at 21 April 2010. The concluded result show that, the determination coefficients are 79 and 86% for the TRMM data and for the digital precipitation model, respectively
Climatology
Behrouz Sobhani; Mohammad Framarzi
Volume 20, Issue 56 , August 2016, , Pages 171-191
Abstract
Crop production ability and its potential are significantly up to climate, topography and land use which are the most important environmental factors. In this study, using climatic data such as temperature, precipitation, number of frost days, sunny hours and relative humidity related to phonology steps ...
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Crop production ability and its potential are significantly up to climate, topography and land use which are the most important environmental factors. In this study, using climatic data such as temperature, precipitation, number of frost days, sunny hours and relative humidity related to phonology steps of saffron growing, Also ground resource data such as topography, land use layers which are prepared by Landsat 8 satellite imagery dated 14/5/2013. Evaluating each of these parameters have been taken in relation to the climate and ecology needs of saffron. Information layers of them were prepared by adjusting data to the surface, and processing them by GIS technology. Multi-criteria decision analysis methods (MCDM), based on vikor were used in order to prioritize and evaluate information layers and their weights in connection with each other. Then layers were weighted based on the criteria and subject model also these layers were overlapped and analyzed in GIS environment. Consequentially, the final layer of land suitability was prepared for saffron cultivation. In this study, 10.23, 45.25 and 45.52 percent of the total area are good, average and weak suitability lands respectively. According to this research, vikor method can have an acceptable function over selecting the fitness values for each class.
Climatology
Yousef Ghavidel Rahimi; Manochehr Farajzadeh Asl; Daryoush Hatami Zarneh
Volume 20, Issue 56 , August 2016, , Pages 239-255
Abstract
The NCP as one of the effective teleconnection patterns in level of 500 hpa have an important role in thermal and hydro-climatic variability in East Mediterranean region. In this study to investigate the correlation between the NCP and maximum temperature fluctuations Iran for a 60 years period (1950-2010) ...
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The NCP as one of the effective teleconnection patterns in level of 500 hpa have an important role in thermal and hydro-climatic variability in East Mediterranean region. In this study to investigate the correlation between the NCP and maximum temperature fluctuations Iran for a 60 years period (1950-2010) have been studied. Pearson correlation analysis as the main method used in this study show an inverse relationship between maximum temperatures and selected stations and NCP index. This shows decrease of temperature in positive phase of the NCP and rise of temperature in negative phase. In terms of time correlation coefficients were calculated and showed a significant negative correlation between the temperature of stations and the NCP in months of January, February, March and almost direct relation most stations in August. At monthly interval in the monthly correlation between stations with 0.342 were computed in January. Seasonal correlation of shows a significant correlation of maximum temperatures in winter to be -0.212. In terms of period, the results indicate a strong correlation between cold period in most stations and mentioned index. Atmospheric circulation in 500 hpa at positive and negative phases showed in positive phase, settlement of deep trough on the Caspian Sea, Iraq, Turkey and Iran, and also the location of Iran in the eastern part of the trough axis on the other hand, indicates establishment of a ridge on the North Sea and Europe which leads to transfer of cold temperatures of northern Europe and its adjacence of polar section to Iran. But on the negative phase placement of Iran beneath the ridge axis leads to the creation of a barotropic atmosphere with weak zonal wind and warm temperatures to Iran. So with blowing warm air from Africa, Arabia and low latitude Iran's temperature rises.
Climatology
nader pir moradian; hossein hadinia; afshin Ashrafzadeh
Abstract
Abstract Prediction and evaluation of meteorological data in effect of climate change is very important especially in water resources management. LARS is a model that generates weather data and predicts weather parameters by downscaling global circulation models (GCM). In this study, in order to evaluate ...
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Abstract Prediction and evaluation of meteorological data in effect of climate change is very important especially in water resources management. LARS is a model that generates weather data and predicts weather parameters by downscaling global circulation models (GCM). In this study, in order to evaluate 15 GCM models performance in simulating the minimum and maximum temperature, radiation and precipitation in Rasht synoptic station (2011-2012), statistical downscaling of each model was performed by LARS model. Then, the mentioned data were predicted on the basis selected GCM models for 2013-2042 and 2043-2072 periods. The results showed that the highest increase in annual average of minimum and maximum temperature will occur during the 2043-2072 periods with 1.3 and 2.0 °C, under A2 scenario, respectively. The amounts of radiation will decrease in future periods for all seasons. The highest decrease (143.4 MJ m-2) of radiation will occur in 2013-2042periods in winter under A2 scenario. The seasonal precipitation will often increase in future periods. The highest increase of seasonal precipitation (55.5 mm) will occur under B1 scenario in 2043-2072 periods for autumn.
Climatology
mohammad ali goorbani; surur poorbabak; hosein Jabari; esmaeil asadi; mohammad hasan fazelifard
Abstract
Abstract Classification of Meteorological stations, causing a large volume of data to be allocated a smaller homogeneous groups, Ease of use in modeling and also can help to spread the information to point to the lack of regional data to Statistics regional statistic. Meteorological stations in ...
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Abstract Classification of Meteorological stations, causing a large volume of data to be allocated a smaller homogeneous groups, Ease of use in modeling and also can help to spread the information to point to the lack of regional data to Statistics regional statistic. Meteorological stations in the region has a crucial role in the management and effective use of information. In this study, 112 stations were analyzed in order to classify regions with fuzzy cluster analysis and Kohonen artificial neural Networks. Four parameters, namely mean annual temperature, longitude, latitude and elevation are considered as the classification criteria for grouping to obtain the optimal number of groups the lowest value of Davies- Bouldin index were used. Demarton climatic zonation was performed to evaluate the spatial distribution of clusters obtained from various methods. The results showed that the fuzzy clustering technique with the Demarton climatic zones is more consistent.
Climatology
hamid galilvand; hosein zarean; hojjat allah yazdanpanah; saeed movahedi; mehdi momeni; nabi allah yarali
Abstract
Abstract Knowledge of past climate needs long-term and accurate climatic data for future planning and predicting. In this study, we reconstructed the average maximum temperature in spring and minimum temperatures in fall and winter by applying the width of annual ringsofQuercusPersica through multiple- ...
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Abstract Knowledge of past climate needs long-term and accurate climatic data for future planning and predicting. In this study, we reconstructed the average maximum temperature in spring and minimum temperatures in fall and winter by applying the width of annual ringsofQuercusPersica through multiple- regression. With this goal in mind, two growth heights were selected in Dena Forests and 40 growth samples from 20 bases in two geographical directions of southwest and northeast were extracted at breast height and measured with AutoCAD software with an accuracy of 3 microns. After cross dating stage, to eliminate non-climate effects, all climatic parameters and tree rings time series were standardized. The calculated Residual Chronology (RES) was calibrated with climatic variations of the period 1881-2011 and positive and significant correlation with the width of growth rings was confirmed. Based on the relations and correlation between the calculated chronology and joint statistical climatic data the reconstruction of annual rainfall was performed and it was found that the average rainfall of the last three decades had a 4 percent increase in comparison to the average rainfall of the last century.
Climatology
mohammad ali khorshiddoost; mojtaba fakhari
Abstract
Abstract One of the most important issues in arid and semi-arid regions is water resources management. Thus the study of the occurrence or non-occurrence of precipitation behavior can improve management water resources in these areas. In this study, the occurrence of days with precipitation in the south ...
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Abstract One of the most important issues in arid and semi-arid regions is water resources management. Thus the study of the occurrence or non-occurrence of precipitation behavior can improve management water resources in these areas. In this study, the occurrence of days with precipitation in the south west of Iran using daily rainfall synoptic stations in the 1994-2009 periods and adapting Markov chain was performed. The frequency matrix, switching matrix and stable matrix as well as continuous rainfall and the rainfall return periods of 2 and 5 days were calculated. The results show that the minimum probability of rain is in the plain area while the highest probability of rainfall belongs to the mountainous area. Also the highest probability of monthly precipitation is in January and the minimum is that of summer. The minimum of return period and the maximum continuous rainfall are in the mountainous stations and the maximum of return period and minimum continuous rainfall are in the plain area. Also unlike the other months, the maximum of probability rainy days in June is in eastern parts of mountains.
Climatology
Rasool Daneshfaraz
Volume 19, Issue 54 , February 2016, , Pages 127-142
Abstract
This study performs a sensitivity analysis to evaluatethe meteorological parametersthat affect daily pan evaporation rate. To this end, five meteorological parameters namely, daily mean temperature, relative humidity, sunshine hours, solar radiation, wind speed and pressure for period of 1386 to 1390 ...
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This study performs a sensitivity analysis to evaluatethe meteorological parametersthat affect daily pan evaporation rate. To this end, five meteorological parameters namely, daily mean temperature, relative humidity, sunshine hours, solar radiation, wind speed and pressure for period of 1386 to 1390 were used at the Tabriz City, Iran. At first, the pan evaporation rate was estimated using Artificial Neural Network (ANN) and the best structure of the ANN was distinguished. Then, weight matrix of selected structure of the network along with the Garson algorithm were used for sensitivity analysis of the input parameters and determine relative importance of the input parameters. The results indicated that the daily mean temperature and relative humidityare the most effective variables. However, the sunshine hours, solar radiation, wind speed and pressure have less effect on the evaporation rate at the Tabriz station.
Climatology
Gholam abbas Fallah Ghalhari; Mehdi Asadi; Alireza Entezari
Volume 19, Issue 54 , February 2016, , Pages 235-251
Abstract
Climate classification and identifying the most effective factors and elements of each area is one way of understanding identity of the climate zones. Therefore, to identify Guilan climate mapping new methods such as factor analysis and hierarchical cluster were performed. For this, we used 20 climate ...
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Climate classification and identifying the most effective factors and elements of each area is one way of understanding identity of the climate zones. Therefore, to identify Guilan climate mapping new methods such as factor analysis and hierarchical cluster were performed. For this, we used 20 climate variables of the 16weather stations in the study area. Then, using interpolation method, a matrix with dimensions of 20×106 data was obtained. Climate mapping of the province with factor analysis showed that the climate of the province is made up of two factors. These two factors are: humid-rain–wind and temperature–cloudy factors. Results also indicated that these two factors explain 99.44 percent of the variance of the primary variables. The contribution of each factor was 64.49, 34.95 percent respectively. Finally, cluster analysis on two climatic factors identified three climatic regions in the provinces. These three regions are: moderate and humid, mountainous, semi humid and cold.
Climatology
Yousef Ghavidel Rahimi; Mohammad Rezaei
Volume 19, Issue 54 , February 2016, , Pages 253-277
Abstract
Heat waves are considered as one of the important climatic hazards in the world and especially in Iran and it seems that, due to intensification of global warming, their occurrence has increased in recent years than in the past. This study has paid attention to quality and quantity evaluation and synoptic ...
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Heat waves are considered as one of the important climatic hazards in the world and especially in Iran and it seems that, due to intensification of global warming, their occurrence has increased in recent years than in the past. This study has paid attention to quality and quantity evaluation and synoptic analysis of heat waves in the KermanProvince. For this purpose, At first, the daily maximum temperature data, in month of July (as the warmest month in the year) was put in a statistical period of 24-years (1986-2009) from meteorological organization, for 4 synoptic stations of Kerman, Bam, Anar and Sirjan. In order to classify heat waves, standardized temperature data and on its basis, anomalies of 0 to 0.75 as a heat wave, 0.75 to 1.5 as severe heat waves, and greater than 1.5 were determined as super heat wave. The threshold values of 43.1, 42.1 and 41.2° C were calculated for all stations, respectively as threshold of heat wave, severe heat wave, and super heat wave and its continuity were considered at least for two days. Accordingly, During Statistical period of study, it was found 7 heat waves, which were, identified within 3 severe heat waves, and 1 super heat wave. Super heat wave in July 1998, was selected For the Synoptic analysis. This three-day wave, with an average temperature of 43/11° C, has been the most severe heat wave in KermanProvince. Results of synoptic analysis of super heat wave indicated that the establishment of Ganges low pressure on the ground and the domination of subtropical high-pressure of azores in high levels and also, high thickness atmosphere on the study area caused the subsidence of warm air and excessive heating of earth's surface, and created them mentioned super heat wave.
Climatology
Peyman Mahmoudi; Mahmood Khosravi; Seyed Abolfazl Masoodian; Bahlol Alijani
Volume 19, Issue 54 , February 2016, , Pages 303-327
Abstract
To identify and detect the frequency variation trend of Iran’s pervasive and semi-pervasive frost days in the current research, minimal daily temperature data of 663 Iranian climatology and synoptic stations were acquired from Iran Meteorology Organization during the time interval between 1962 ...
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To identify and detect the frequency variation trend of Iran’s pervasive and semi-pervasive frost days in the current research, minimal daily temperature data of 663 Iranian climatology and synoptic stations were acquired from Iran Meteorology Organization during the time interval between 1962 and 2004 for October to April months. Following data acquisition, Iran’s isothermal maps for each day starting from 1.1.1962 until 31.12.2004 (9116 days) were prepared using Kirging interpolation technique in order to construct the database of the county’s minimal temperature. In the next step, frosts were classified in three types based on a spatial principle: pervasive frosts (simultaneous occurrence in more than 65% of Iran’s surface area), semi-pervasive frosts (simultaneous occurrence in 25% - 65% of Iran’s surface area), and local frosts (simultaneous occurrence in less than 25% of Iran’s surface area). Then, frequency of pervasive and semi-pervasive frost days were analyzed in three scales including monthly, seasonal, and yearly using two estimation techniques of slope SENSE and linear regression.
Results indicated that frequency of pervasive frosts in Iran held a statistically significant decreasing trend in December and January months, during winter, and also, in annual basis. But, for semi-pervasive frost days, it was observed that variation was significant only in January having a positive trend. It signifies that number of days with semi-pervasive frost increased during the 43 years under study. Therefore, number of semi-pervasive frost occurrences increased while number of pervasive frost occurrences decreased in January. The same rule holds for other scales i.e. monthly, seasonal, and yearly basis.
Climatology
Mohamad Reza Aphsharei Azad; Halea Pouraky
Volume 19, Issue 53 , September 2015, , Pages 1-24
Abstract
Rivers across the nation in terms of conservation, utilization and development of as well as quantitative and qualitative evaluation of favorable river conditions for fish to be used. This study is analysis of factors that is necessary to apply physiographic models of river which have role on topology ...
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Rivers across the nation in terms of conservation, utilization and development of as well as quantitative and qualitative evaluation of favorable river conditions for fish to be used. This study is analysis of factors that is necessary to apply physiographic models of river which have role on topology of stations of fish culture(salmon), in addition to factors which have been used currently in this field, Sham rood river has been studied in terms of physiography. Results of survey among various factors are indicating importance of physiography of studied location that is usable for constructing workshops of fish culture; Sham rood river is regarding to biologic and frequency indices, its potential power to produce fish is 348 kg.hec. This production is high since Farvardin until Shahrivar and then Khordad has highest amount of fish production. Effective factors include physiographic patterns such as area and perimeter, form of basin, height, inclination, and direction of inclination. These results in analysis of future procedures show condition of topology of fish culture pools' construction and physical and mechanical elements of fish culture such as PH of water, velocity of water flow, light effect, degree of water turbid, suspension solids, solidity of water, electric conduction of water (EC), chemical materials, water salinity, rate of required water show biological factors. Finally, check the condition of steep mountainous watersheds for fish with cold water and put the channel maps, political spots, lithology, slope, aspect factors needed to put them together with the salmon farming appropriate the construction of stations and half fish and unfavorable conditions for fish and plant construction has been determined ..
Climatology
abasali Arvin
Volume 19, Issue 52 , June 2015, , Pages 25-42
Abstract
Variations of ozone layer that measure by name of total ozone (TO) oscillation are one of the modern humane concerns as one of causes or manifestations of climate change. In this research total ozone oscillation in relationship with Sea Surface Temperature (SST) in Pacific Ocean has been studied. For ...
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Variations of ozone layer that measure by name of total ozone (TO) oscillation are one of the modern humane concerns as one of causes or manifestations of climate change. In this research total ozone oscillation in relationship with Sea Surface Temperature (SST) in Pacific Ocean has been studied. For this aim monthly mean data from the satellites in point by 1*1.25 degree of geographical distance and monthly mean of NINO1+2, NINO3, NINO4 and NINO3.4 indices have been used. The results show that total ozone in positive\negative occurrence of SST has been increased\decreased in all Iranian areas. The asynchronous relation of effects SST indices have been tested on (TO). The strongest relations in lag time of months 5, 1, 5 and 2 respectively are for NINO1+2, NINO3, NINO4 and NINO3 indices. The correlation of NINIO1+2 with TO are better than other indices and the strongest correlation was in west and northwest of Iran. The average of synchronous and asynchronous (5 months lag time) correlation coefficient between NINIO1+2 with TO on all areas of Iran was respectively r=+0.55 and r=-0.621. The in synchronous correlation was direct and significant at 0.05 level in 86 precent of areas of Iran but asynchronous correlation was indirect and significant at 0.05 level The relation of NINO4 with (TO) was the weakest correlation in other indices.
Climatology
nahideh Jahedi; mohammadali Ghorbani
Volume 19, Issue 52 , June 2015, , Pages 63-63
Abstract
Being aware of decreasing or increasing trend of precipitation and discharge in watersheds has very important role in water resources management and the subjects relating to water engineering. In this study, the trend of precipitation and discharge at Qara-su River Basin in Ardebil has been studied in ...
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Being aware of decreasing or increasing trend of precipitation and discharge in watersheds has very important role in water resources management and the subjects relating to water engineering. In this study, the trend of precipitation and discharge at Qara-su River Basin in Ardebil has been studied in monthly, seasonal and annual timescales over the period from 1351 to 1382. For investigation of the existence or absence of a trend, Mann-Kendall test was used by detecting effects of all auto correlations coefficients, and Sen’s estimator was used at different significant level to evaluate the magnitude of the test. The results of the calculated values for precipitation and discharge data set indicated that the trend of the Qara-su River discharge was decreasing for both stations in annual timescale. Also, decreasing trend of discharge dataset was found for seasonal timescale in spring, autumn and winter in which significant trend belonged to winter season. Maximum value of decrease for discharge is for Doustbiglo station in spring (-0.62 m^3/s), and the minimum value of decrease for discharge in summer for this station, too. Furthermore, there was not significant trend for precipitation dataset in monthly, seasonal, and annual timescales.
Climatology
Mahmood Khosravi; Nematollah Safarzaie; Mohsen Armesh
Volume 19, Issue 52 , June 2015, , Pages 113-140
Abstract
Frost is one of the natural disasters that is usually are associated with financial losses and even mortality. The atmospheric circulation systems have a main role in the occurrence, severity and spatial distribution of frost especially in temperate regions. The purpose of this research is the detection ...
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Frost is one of the natural disasters that is usually are associated with financial losses and even mortality. The atmospheric circulation systems have a main role in the occurrence, severity and spatial distribution of frost especially in temperate regions. The purpose of this research is the detection and investigation of synoptic conditions simultaneous with occurrence of winter frosts in Sistan region. The method used in this analysis approach is peripheral circulation. For these purposes, two databases (surface and atmospheric) were required. For surface data, climate data from synoptic weather stations of Zabol and Zahak were used as a representative of the regional climate. The longest and most severe frost was selected during the last decade (2010-2000). Second database of sea level data and maps of 850 and 500 Hp levels was prepared from the National Center for Environmental Prediction (NCEP) and National Center for Atmospheric Research (NCAR). Spatial coverage of weather data is between 30 until 90 degrees east longitudes and 10 until 50 degrees north latitude. For representing the weather stream lines maps, Grads software was used. The results showed that cyclonic activity on the Balkhash Lake prepared the situation for downfall of cold air of high latitude and western flow of trough to region and caused frost in the Sistan region. Transferred axis of trough at the eastern regions and the above conditions caused more frost persistence. The most severe frost in Sistan region tll, place in the western part of trough and the flux of northern cold air. The factor that has created these conditions is the pressure gradient between the southern and northern regions of Sistan, especially South East of Sistan low-pressure system which led to the establishment of west part of trough to the region.
Climatology
ali Mohammad Khorshiddoust; Behrooz Sobhani; Kamel Azarm; Jamal Amini
Volume 19, Issue 52 , June 2015, , Pages 141-161
Abstract
Canola is the world third leading oil seed after soybean and oil palm by producing 15 percent of the global plant oil. Climate, topography and lands capability are the most important environmental factors on which the crop production capability in a region depends. Therefore by evaluating these factors ...
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Canola is the world third leading oil seed after soybean and oil palm by producing 15 percent of the global plant oil. Climate, topography and lands capability are the most important environmental factors on which the crop production capability in a region depends. Therefore by evaluating these factors one can identify suitable lands for canola cultivation. In the present study, the climatological data such as temperature, precipitation, growth degree day, relative humidity, freezing days, and sunshine hours were collected from the West Azerbaijan province synoptic and rain gauge stations (since their installation untill 1388) which were associated with the phenologic stages of canola growth. In addition to the climatological data, earth resources like topographic layers, lands capability, soil depth and land-use were analyzed focusing on the climatological and ecological requirements of canola. After generalizing the data and processing by using ArcGIS, their corresponding information layers were derived. In order to prioritize and assess the criteria and information layers in relation to each other, the multi criteria decision method was employed based on analytical hierarchy process. Then, combination and spatial analysis of the information layers using TOPSIS model and GIS capabilities were done and the final capability ecological evaluation layer for canola cultivation was produced. Based on the obtained results, the province lands were divided into four categories of highly suitable (%18.6), suitable (%34.4), moderate (%32.1) and weak (%14.7) lands on the basis of the environmental and climatologocal potentials for canola cultivation.
Climatology
Bahlol Alijani; Hasan Farajzadeh
Volume 19, Issue 52 , June 2015, , Pages 229-256
Abstract
Natural environment is regulated according to the climatic conditions. Human communities are forced to adjust themselves to these conditions. Identifying the intensity, frequency and timing of climatic events can help solve the environmental problems and ease the coherent planning to mitigate these events ...
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Natural environment is regulated according to the climatic conditions. Human communities are forced to adjust themselves to these conditions. Identifying the intensity, frequency and timing of climatic events can help solve the environmental problems and ease the coherent planning to mitigate these events changing behavior. To achieve this objective in the Northwest of Iran, daily minimum and maximum temperature data from 13 stations were obtained from the Meteorological Organization of Iran in the quality control format for the existing data period. Sixteen Extreme indices were extracted by RClimDex package and their changing behavior was checked by Mann – Kendall method. The results showed that the frequency of cold indices decreased but the frequency of extreme warm indices increased during the study period. According to the results of wavelet analysis all the extreme cold indices showed a significant periodic fluctuations of 2 to 4 years. Among the warm indices only the warmest days index (TXx) showed 2 to 4 years fluctuation and the number of tropical nights (TR20) exhibited 4 to 8 years of significant fluctuation.
Climatology
Rasool Mirabbasi Najafabadi; yaghoob Dinpashoh
Volume 19, Issue 52 , June 2015, , Pages 277-301
Abstract
The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); ...
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The aim of this study is the analysis of surface wind speed in monthly and annual times scales in Iran using four different versions of the Mann-Kendall method: i) conventional Mann-Kendall method (MK1); ii) Mann-Kendall method following removing the effect of significant lag-1 auto-correlation (MK2); iii) Mann-Kendall method after the removing the effect of all significant auto-correlation coefficients (MK3); and Mann-Kendall method with considering the Hurst coefficient (MK4). Data used here are wind speed records in both monthly and annual time scales in the period of 1966-2005. For this purpose, 22 stations were selected across Iran’s area. Nonparametric Sen’s method was used for estimation of wind trend line slope. Results showed that although a combination of positive and negative trends observed both in monthly and annual time scales, however, the number of stations having the negative trends were more than that of the positive trends. In the annual time scale, the strongest negative trend line slope was -0.074 ms-1y-1 belonging to Fasa station, and the strongest positive trend line slope was 0.141 ms-1y-1 belonging to Zabol station. In monthly time scale, the strongest negative trend line slope was -0.1 ms-1y-1 observed in Fasa station and the the strongest positive trend line slope was 0.18 ms-1y-1 observed in Zabol station. Results showed that the median of the trend line slopes for all months (except February and November) was negative. Therefore, in general, it can be concluded that in the most of stations in Iran wind speed trend in all months (except February and November) was negative.
