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.
Climatology
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.
Climatology
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.
Climatology
Nafiseh Rahimi; Saeed jahanbakhsh; Brooman Salahei
Volume 23, Issue 70 , March 2020, , Pages 145-167
Abstract
Strong winds are one of natural disasters that sometimes cause enormous Financial and physical damages. Since northwest of Iran and specially Ardabil Province is one of windy regions, this study tried to identify synoptic patterns which bring strong winds. Through considering equal and threshold wind ...
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Strong winds are one of natural disasters that sometimes cause enormous Financial and physical damages. Since northwest of Iran and specially Ardabil Province is one of windy regions, this study tried to identify synoptic patterns which bring strong winds. Through considering equal and threshold wind speeding over 28 knots per second, 783 days identified as wind crashing days in Ardabil province. Then by data component- based analysis of 500hPa geo-potential height of the 783-days detected seven components which explain 92% of variance. Finally by clustering seven components identified ten patterns as synoptic patterns that are responsible for Strong wind of Ardabil province. The survey of topographic arrangement of these patterns indicates the rise of trough and ridge levels to these patterns. This means that the patterns consists of, mainly, trough, ridge, or combination of both and aren’t observed other systems such as cut off, block systems, etc. Although mentioned systems may be observe in individual patterns of each of the 783 days, but the systems aren’t responsible for the dominance and influence. The temporal distribution patterns show that two patterns, 6 and 7which occurs in the summer, has a similar system at 1000 hPa level when it compares with other models which occur in winter, spring, fall. What's notable, reversal of location position of pressure systems, 1000 hPa, in two patterns of summer, so that a low pressure instead of high pressure is over the Zagros and a high pressure instead of low pressure is over the Caspian Sea.
Climatology
Mohammad Reza Azizzadeyya Varzegan; khadijeh javan
Volume 23, Issue 70 , March 2020, , Pages 227-246
Abstract
One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend ...
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One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend of precipitation extremes in Lake Urmia basin and to investigate their relation with Teleconnection patterns. For this purpose, daily precipitation data of 7 synoptic stations in the basin during 1987-2014 was used. 11 extreme precipitation indices were extracted using the RClimDex and their trends were calculated by non-parametric Mann-Kendall test. Then the relationship between these indices with Teleconnection patterns was determined by the Pearson correlation coefficient. The results of time series analysis showed that all extreme precipitation indices in Lake Urmia basin have decreasing trend exept consecutive dry days (CDD). The spatial distribution of trend in extreme indices showed almost all indices have a significant trend at the 5% significance level in basin. There is no significant trend in consecutive dry days (CDD). The changes in extreme precipitation could be affected by the El Niño-Southern Oscillation (ENSO), Southern Oscillation Index (SOI), East Pacific-North Pacific (EP-NP), Madden and Julian Oscillation (MJO) and Pacific Decadal Oscillation (PDO).
Climatology
ali akbar rasouli; elnaz ostadi; mohammad reza aziz zade
Volume 23, Issue 69 , December 2019, , Pages 87-103
Abstract
The consequences of climate change in drought areas such as Iran, temporal and spatial changes are the distribution and concentration of rainfall, which can affect water resources. On the other hand, increasing the concentration of rainfall can causing hazards such as floods . The importance of the issue ...
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The consequences of climate change in drought areas such as Iran, temporal and spatial changes are the distribution and concentration of rainfall, which can affect water resources. On the other hand, increasing the concentration of rainfall can causing hazards such as floods . The importance of the issue of distribution and concentration of rainfall has encouraged researchers to study in this regard. Concentration Index (CI) is a method which is used to study the distribution and concentration of rainfall. This study was performed to calculate and analyze 23 station daily precipitation concentration index in Northwest of Iran during 1951 to 2015. In this research range of CI values calculated between 0.57 for Khoy station to 0.67 for Maku station and average 0.61 for all station. CI map obtain from values Interpolation and showed that the Northwest part of the study area with Maku station depute, compared to other regions, especially in central areas such as Tabriz station is not uniformly distributed. Also Northwest area with an average of 0.61 compared with an average CI of Iran ( 0.64) is more evenly precipitation distributed throughout the year.
Climatology
Jaber Soltani; masoud ahmadi nik; Ahmad Ahmadinik
Volume 23, Issue 69 , December 2019, , Pages 127-147
Abstract
Reference evapotranspiration is one of the necessary parameters to determine crop water requirements and irrigation planning. Having accurate estimates of this parameter is essential for planning and managing of water resources. Several experimental models have been proposed to estimate evapotranspiration. ...
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Reference evapotranspiration is one of the necessary parameters to determine crop water requirements and irrigation planning. Having accurate estimates of this parameter is essential for planning and managing of water resources. Several experimental models have been proposed to estimate evapotranspiration. According to the spatial variability of climatic parameters, using remote sensing method that considers these changes is very favorable. Among the most widely used models that accurately estimate evapotranspiration using remote sensing, can be mentioned wavelet model. In this regard, the purpose of present study is to evaluate the accuracy of wavelet models to estimate the reference evapotranspiration using parameters derived from satellite images contains the Earth's surface temperature and amount of water vapor in the atmosphere. In this study, used atmospheric and satellite images data of four station contains Anar, Kerman, Rafsanjan and Shahrebabak to develop and evaluate wavelet models. In the first scenario, temperature, in the second scenario, atmosphere water vapor parameter and in third scenario, both parameters simultaneously was used as the model input. Results of this study showed that despite the high accuracy of models in different scenarios, the wavelet model use two-parameters, temperature and steam simultaneously (third scenario), with a coefficient of 90% compared to other models had the more accurate.
Climatology
esmaeil abbasi; mahdi khazayi
Volume 23, Issue 69 , December 2019, , Pages 175-190
Abstract
One of the most devastating phenomena of meteorology which varies extensively in spatial and temporal extent and manifests itself at various scales, is thunderstorms. The purpose of this study was to identify and analyze such destructive storms over a period of 25 years (1986-2010) at the synoptic station ...
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One of the most devastating phenomena of meteorology which varies extensively in spatial and temporal extent and manifests itself at various scales, is thunderstorms. The purpose of this study was to identify and analyze such destructive storms over a period of 25 years (1986-2010) at the synoptic station of Kermanshah. The data used in this research includes daily rainfall data and codes related to meteorological phenomena, dry temperature, dew point, relative humidity, wind direction and wind speed for calculation of instability indices, geopotential height parameters, specific humidity, vertical velocity, and zonal and meridional components. The results showed that during the statistical period of the study, three extreme thunderstorms occurred in the study area during the statistical period of 25 years. The study of instability indices indicates that these indices are in the strong and suitable category for the occurrence of thunderstorm phenomenon; in addition, the dynamics of the atmosphere at the time of the occurrence of this phenomenon indicates the presence of a very deep trough and negative abnormalities in the west of the studied region and positioning of the left half of the Jetstream of levels of 500 and 850 millimeters on the studied area. Following this phenomenon, the thunderstorm intensely affected the region by its destructive effects with the formation of clouds of cumulus and lightning, and finally, heavy rainfall. However, it should be mentioned that for two cases, that is, the phenomenon of February 4, 2007 and December 12, 1991, they experience a more unstable climate due to the average circulation patterns compared to the other identified case, i.e. the phenomenon of April 17, 1991.
Climatology
Hossein Asakereh; Mokhtar Fataheyan
Volume 23, Issue 69 , December 2019, , Pages 191-211
Abstract
Atmospheric circulation is a fundamental factor in determining the climatic conditions of every region (Mofidi and Zarrin, 1391). Therefore, the climate framework of every location is based on large-scale systems. One of the most obvious and permanent tropical landscapes along the northern and southern ...
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Atmospheric circulation is a fundamental factor in determining the climatic conditions of every region (Mofidi and Zarrin, 1391). Therefore, the climate framework of every location is based on large-scale systems. One of the most obvious and permanent tropical landscapes along the northern and southern tropical hemisphere as cores of high-pressure centers or high-altitude bands is called the "tropical high-pressure" system. The subtropical high-pressure cores are known in various areas under various names (such as high-pressure azure, high-pressure Saudi, etc.). For example, Mason and Anderson (1963) define the most intense and permanent anticyclone as the Asian Anticyclone studying the two levels of 100 and 50 hPa and by investigating daily weather-condition maps during 1957-59. Since the spatial-temporal variance and intensity change of this system causes anomalies in regional and global circulation and consequently climatic anomalies, therefore, due to the geographical location of Iran relative to the climate of the above system, the spatial variations of this system have significant effects on Iran.
Climatology
Mostafa Karimi; Faramarz Khoshakhlagh; ali akbar shamsi por; fahimeh noruzi
Volume 23, Issue 69 , December 2019, , Pages 233-255
Abstract
Large-scale circulation patterns are controlling climatic conditions and especially precipitation of the area. The purpose of the study is investigating the relationship between circulation patterns of Arabian subtropical anticyclone and Iran precipitation. For this reason, was used re-analysis data ...
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Large-scale circulation patterns are controlling climatic conditions and especially precipitation of the area. The purpose of the study is investigating the relationship between circulation patterns of Arabian subtropical anticyclone and Iran precipitation. For this reason, was used re-analysis data of geo-potential height form European Center for Medium-Range Weather forecasts (ECMWF), with spatial resolution of 1*1 degree and correlation distance cluster analysis. Circulation patterns at 30 to 80 degrees the East longitudes and5 to 30degrees north latitudes and the period of11years (2000- 2010) was calculated. The results showed that the patterns in terms of occurrence were divided the patterns of the cold period, the warm period and the transition period. During the cold period anticyclone is located at down latitudes on the Arabian sea and Gulf of Aden and have precipitation more areas of Iran that maximum amount of precipitation is related to the second pattern. In the patterns of transition period Arabian anticyclone sent a southwest clockwise current in to the trough East Mediterranean is effective in the occurrence of precipitation in the area of North and Northwest of the country. In the patterns warm period the anticyclone caused the anticyclone conditions on country and has been as a barrier to entry precipitation systems.
Climatology
KARIM AMININIA; Ali Mahmoudei
Volume 23, Issue 68 , September 2019, , Pages 23-45
Abstract
One of the things done in the field of synoptic climatology is air typology. An air typology represents types of air that are similar enough in terms of particular atmospheric variables. The emergence of an air type in a certain area, on one hand, depends on the air masses entering to the area, and on ...
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One of the things done in the field of synoptic climatology is air typology. An air typology represents types of air that are similar enough in terms of particular atmospheric variables. The emergence of an air type in a certain area, on one hand, depends on the air masses entering to the area, and on the other hand, reflects the geographic conditions (roughness, adjacency to the masses of water, etc.) of that area. Since the geographic conditions of each area are usually constant, the difference in air types that come and go in the region is a function of the air masses that enter the area. Characteristics of the air masses while moving and crossing different areas, change, adjust and turn into another air. Given the fact that the repetition of air types determines the climate in an area, it is very important to identify the types of air. This is because without knowing the types of air dominating an area, management and planning will be very difficult and even impossible. This is while by identifying air types, it will possible to identify possible types of natural disasters in different sectors of agriculture, industry, etc. and prevent its damages. Since each type is related to circulation patterns, recognizing the characteristics, severity, and frequency of each type can show us their remaining time and duration of their domination, and help us in planning
Climatology
gholam hassan jafari; Hazhir Mohammadi
Volume 23, Issue 68 , September 2019, , Pages 47-69
Abstract
Changes in the base levels are the most important factors of forms and processes’ imbalance in drainage basins. Ghezel Ozan basin, which is the sub-basin of Caspian Sea, has had many effects on base level fluctuations. In this study, Channels and Lithology were evaluated using GIS software and ...
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Changes in the base levels are the most important factors of forms and processes’ imbalance in drainage basins. Ghezel Ozan basin, which is the sub-basin of Caspian Sea, has had many effects on base level fluctuations. In this study, Channels and Lithology were evaluated using GIS software and topographic and geological maps. Using evidences, the base level changes including the capture and diversion of convergent radial rivers and channels of Bijar geo-neuron in Qezal Oazan Basin were identified. Also, the relationship between branch and length of the channels in Bijar sub-basins was investigated using the fractal geometry theory and Horton- Strahler stream ordering method and their fractal dimension was calculated. The results show that the effects of changes in local base levels of Bijar hole can be traced as aggregate levels in the alluvial plains of 6 sub-basins of Angouran-Chay, Hassanabad Yasukand, Yol-Kashti, Ghorveh and Dehgolan, Garmab and Sujasrud. The prospecting process is visible in the center of the hole. At elevations of 1561, 1540 and 1515 meters in Bijar hills, 3 lake terraces have been observed. The fractal number of 2.12 of Bijar basin indicates that the whole basin is in a relatively moderate condition and the retardation erosion in the branches is going to be stopped. In the two sub-basins of Yol-Keshti and Ghorveh-Dehgolan, fractal dimension of less than 2 shows that the coefficient of branching is greater than the basin area. At the head of the water at the Angoran Chay, Sujasrud and Garmab sub-basins, the branches are still developing and retreating. Hassanabad Yasukand sub-basin with the highest fractal number among the sub-basins (3.25) reaches its maximum balance and the lowest erosion is dominant in its branches. Investigating the relationship between fractal dimensions and branching ratio with the area of the studied basins indicates a reverse and negative relationship.
Climatology
Ali Mohammad Khrshieddoust; Hamid Mirhashemi; Mousa Nazari
Volume 23, Issue 68 , September 2019, , Pages 71-90
Abstract
Evaporation is one of the important factors in the hydrological cycle and is one of the determinants of energy equilibrium at ground level and water balance, which is required in various areas such as hydrology, hydrology, agriculture, forest management, and management of water resources (Sanei Nejad ...
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Evaporation is one of the important factors in the hydrological cycle and is one of the determinants of energy equilibrium at ground level and water balance, which is required in various areas such as hydrology, hydrology, agriculture, forest management, and management of water resources (Sanei Nejad et al., 2011). In this regard, one of the basic data in designing irrigation and drainage networks is the amount of evaporation power in each region. Because the design of transmission networks, such as drainage or drainage channels, as well as other parts of water design, depends on the amount of water required by the evaporation phenomenon (Jahanbakhsh et al., 1380). In general, evaporation hydrology is generally referred to as the phenomenon of water It simply turns steam into a physical process.
Climatology
somyyeh Soltanei; Soheila Zareh; Mahdei Taze
Volume 23, Issue 68 , September 2019, , Pages 157-177
Abstract
Rainfall erosivity factor is the most important factor influencing soil erosion. Various indicators has been developed to quantify it. Selection the appropriate index due to ecological conditions is necessary. Therefore mapping rainfall erosivity and awareness its changes, plays an important role in ...
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Rainfall erosivity factor is the most important factor influencing soil erosion. Various indicators has been developed to quantify it. Selection the appropriate index due to ecological conditions is necessary. Therefore mapping rainfall erosivity and awareness its changes, plays an important role in soil conservation, erosion control and land management. The purpose of this study is the selection of the best geostatistic method for mapping the rainfall erosivity factor in Fars province. In first step Fournier factor was calculated for 42 stations in Fars province and its surrounding and was determined the best geostatistic method using IDW, GPI, LPI, RBF, Ordinary and Simple and was prepared zoning map for Fournier factor. The results showed that among the various geostatistic techniques, RBF method (Thine plate Spline) is the best method for mapping rainfall erosivity factor in Fars province. Also, Noorabad city in northwest of province with an average of 31.6 mm Fournier and Izadkhast city with 8.67 were determined as the highest and lowest of the erosivity index. Also, Fournier index has increased from the East to the West as 46% of the province has a low erosion and 3% of the province has been high erosion that have had the highest and lowest levels.
Climatology
Behrooz Sari Sarraf; Shoaieb Abkharabat
Volume 23, Issue 68 , September 2019, , Pages 179-193
Abstract
As a core of wind speed, Low Level Jet (LLJ) of the Persian Gulf is made on the Persian Gulf and its surrounding in the low levels of the atmosphere during the hot period of the year. Known as north wind, this jet appears in the body of a more extensive current of wind with the northern, northwestern, ...
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As a core of wind speed, Low Level Jet (LLJ) of the Persian Gulf is made on the Persian Gulf and its surrounding in the low levels of the atmosphere during the hot period of the year. Known as north wind, this jet appears in the body of a more extensive current of wind with the northern, northwestern, southern, southeastern direction. North wind often blows from the mountainous regions of Turkey and Iran to the southern regions. Except for topographic reasons, the formation of this wind is influenced by hollow topography of low regions of Mesopotamia and Khouzestan appearing as a corridor. Reaching the Persian Gulf, this phenomenon is intensified as the water area of the Persian Gulf is besieged as a low hollow by Zagros Mountains and Arabic Peninsula aggravating the wind.
Climatology
Saeed jahanbakhsh; yagob din pazhoh; mohammad hossein aalinejhad
Volume 23, Issue 67 , April 2019, , Pages 91-107
Abstract
According to the importance of snowfall in supplying water of different regions especially mountainous areas, accurate estimation of snow water equvallent and changes of its coverage would be effective in agriculture, energy, management of reservoir and flood warnings. In this study runoff orginated ...
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According to the importance of snowfall in supplying water of different regions especially mountainous areas, accurate estimation of snow water equvallent and changes of its coverage would be effective in agriculture, energy, management of reservoir and flood warnings. In this study runoff orginated from snow melting in ShahrChay basin under the terms of climate change calculated. For this purpose, snow cover for water year of 2012-2013 were extracted in ENVI software by using daily images of Modis satellite.Then, GIS software the physiographic specification of the basin was obtained. In the next step, data of snow cover, meteorological variables and other necessary parameters to SRM model provided as an input of model and run_off from snow melt was simulated. Then output of the 6 models of atmospheric general circulation with title of 3 scenarios nomely A1B , A2 and B1 converted to a downscaleing by using LARS-WG model. By comparing the output of 6 models in the future period to period based on monthly statistical, the best model and scenario for generation of air temperature and precipitation data in the period 2030-2011 were selected. As a result the HADCM3 model under the scenario A1B was used for generation of precipitation and the MPEH5 under scenarios A2 was used for generation of temperature data. In order to estimate the rate of change of runoff orginated from snowmelt rate of change of monthly data of air temperature and precipitation of the base time period as well as future time period under selected model and scenarios was entered to SRM model in simulation time period. Results for all of the scenarios show that runoff orginated from snowmelt in late spring will be reduced. The peak flow appeared earlier in comparison with base time period and its value would be larger than base time period.
