Dr Elham Mobarak Hassan, Dr Ebrahim Fatahi, Dr Abass Ranjbar Saadat Abadi, Dr Nasim Hossein Hamzeh,
Volume 23, Issue 71 (12-2023)
Abstract
The Great Khorasan in northeast Iran has a variety of surface structures and plains and high peaks, but due to its vicinity to the deserts of Afghanistan and Turkmenistan, it is affected by dust all the time, especially in summer. The purpose of this study was to simulate summer dust in this region by RegCM model. For this purpose, during the period 2000 to 2017, three extreme dust events were selected. The satellite image used to confirmed dust mass presence and then the synoptic structure was analyzed. Finally, the simulation results of RegCM 4.6 model were compared with the observational data including the horizontal visibility and aerosol optical depth (AOD) of Aqua satellite. The synoptic analysis showed that during the summer, low thermal pressures form in the southern Afghanistan and high pressure in the north. This structure lead to the development of north and northeast winds with speeds of 12 to 21 m / s and dust emission on the eastern border of Iran and western Afghanistan. Investigation of RegCM accuracy done by visibility, Aquas’s AOD showed that model performance in South Khorasan is better as Razavi Khorasan. The highest correlation coefficients of AOD of model and horizontal visibility were obtained at Khorasan central stations including Gonabad, Ferdows, Nahaband and Ghaen at -0.82, -0.77 and -0.44 respectively. RegCM model performed a better dust simulation in severe dust with a horizontal visibility down to less than 1000 m, high continuity and horizontal extension. Overall, the RegCM model underestimates the AOD value for the Aqua satellite algorithm.
Maryam Saghafi, Gholamreza Barati, Bohloul Alijani, Mohammad Moradi,
Volume 23, Issue 71 (12-2023)
Abstract
Precipitation is a phenomenon resulting from complex atmospheric interactions and among climatic events, due to its vital role, it has special importance. The importance of precipitation durability, especially in arid and semi-arid regions, which includes most of Iran, is greater than its volume. The purpose of this study is to identify Iran's precipitation areas in terms of precipitation durability and its characteristics in each area. In order to investigate the durability of Iran's precipitation and to define a precipitation day as " a day with equal precipitation or greater than 0.5 mm", used from daily precipitation data of 80 synoptic stations of the country during the 6 cold months of the year from October to March in a period of 30 years (2016 - 1987). Setting data in daily tables in the first step, made possible to program in MATLAB environment to separate precipitation in ten groups from "one day" to "ten days" and in the second step in SPSS environment based on frequency characteristics, amount and precipitations average in the mentioned groups was done by the method of Ward merging and clustering. The process of the clustering on Iran's durability precipitation showed that there are seven almost homogeneous precipitation zones in Iran; the geographical arrangement of Iran's precipitation areas, reveals the dependence of Iran's precipitations amount on roughness, the path of precipitation systems, its proximity to humidity sources, and the effect of the sea. In terms of area’s location, it can be said that; the settlement of the four zones in the western half of Iran, despite its small size in front of the eastern half, is a reason for its heterogeneity.
Mohamad Hosein Hoseini Rozbahani, ,
Volume 23, Issue 71 (12-2023)
Abstract
Wheat is the main human food that is consumed directly. Recognition of climatic parameters and study of climatic needs of crop plants is one of the most important factors in the production of rainfed wheat. This study is due to the importance of climatic parameters in rainfed wheat production and also due to the potential of rainfed rainforests in Tajikistan, including Ryan Panjkent and Qa in Wadi Zarafshan. The data used in this study were collected through the Tajik Meteorological Department and the Tajik Ministry of Agriculture and the Pentecostal Agricultural Office in the field and in libraries. In the first step, the data were checked for homogeneity and uniformity. In the next step, using Lars Wg software using HadGEM2-ES series models and three scenarios of RCP26, RCP45, RCP85 in the period 2011-2050, the Lars model's ability to predict the climatic variables of Panjkent station was evaluated and then the data. The prediction was evaluated with observational data and also through Anova correlation and test between climatic parameters and production of rainfed wheat per hectare by Toronto White Climate Method. Connection results between climatic parameters and rainfed wheat production Using the analysis of variance (F) test and comparison with the table of coefficients of F showed; There is a significant relationship between rainfall in May and maximum temperature in June with wheat production and also rainfall in October, maximum temperature in November with rainfed wheat production in Panjkent station, there is no significant relationship per hectare.
Fahimeh Shakeri, Gholamabbas Fallah Ghalhari, Hashem Akbari, Zahra Hejazizadeh,
Volume 24, Issue 72 (3-2024)
Abstract
In this research, the sensitivity of the meteorological elements (such as mean temperature, relative humidity and wind speed) to different physical parameterizations in the numerical forecast model (WRF) was evaluated to simulate the climate of the city and adjust the Urban Heat Island of the study area.To study urban environmental issues, the Urban Canopy Model (UCM) was coupled to the WRF model. Several experiments were performed to achieve optimal configuration for simulation in the period from 18-21 August 2016 in the stable atmospheric conditions in summer. Selection of the most appropriate configuration with the least error is proposed as an appropriate setting for urban climate simulations and the study of Urban Heat Island (UHI). Increasing surface reflections to reduce UHI in the range was applied. Two indices of Root Mean Square Error (RMSE), and Mean Bias Error (MBE) were used to evaluate the predictive performance of the model and its corresponding observational values. The results showed that in the province of Tehran, in general, all configurations estimate the air temperature and wind speed less than real and relative humidity more than the actual value. In Alborz province, all configurations estimate the air temperature and wind speed more than real and relative humidity less than real value. By increasing the reflection of urban levels, the mean temperature of Tehran and Alborz provinces decreases 0.6 and 0.2 ° C, respectively. Wind speed, especially in urban areas, increases somewhat. We also see an increase in relative humidity (especially in urban areas) in the studied areas.
Kaveh Mohammadpour, Mohammad Saligheh, Tayeb Raziei, Ali Darvishi Bloorani,
Volume 24, Issue 72 (3-2024)
Abstract
Mineral Dust, the most important type of aerosol, has a significant direct and indirect role in weather and climate. In this case, it intend to investigate the capability and capability of MACC model validated by MODIS for detection of dust episodes in the Kurdistan province during 2003-2012. To achieve that, we analysis satellite and model data using Man-Kendall trend and statistical tests. The results of the temporal distribution indicated that the mean Aerosol Optical depth (AOD) in 2008 was 0.36 and its lowest was 29.04 for 2004. In addition, average AOD in menthioned year was 0.036, 0.335, 0.385, 0.377 and 0.3368 for the cities of Sanandaj, Saqez, Ghorveh, Kamyaran, Marivan, respectively. The spatial distribution of AOD average in different seasons showed that winter and autumn had the lowest amount and spring, and summer season had the highest AOD. AOD's monthly spatial distribution showed that high dust belonging to April-August period to covers completely interested area.The results of the Man-Kendall test showed that the area had a significant positive trend in the spring season throughout the province and the summer season in the east of the province. Therefore, the spring season in the area known Extreme Season and June 19, 2009 between the five days of the dust extreme is as an extreme episode with an average AOD of 1.16 and a horizontal visibility of less than two kilometers that it have the highest and most widespread mineral dust. In general, the results of the MACC with multidimensional approach showed that optical depth (AOD, DOD) is a more appropriate criterion than horizontal visibility in determining dust storm.
Mr Jaefar Derakhshi, Dr Behroz Sobhani, Dr Saeed Jahanbakhsh,
Volume 24, Issue 72 (3-2024)
Abstract
In this study, the prediction of precipitation and temperature values using the general atmospheric circulation models during 1964-2005 is investigated. Climatic data including daily values of total precipitation and mean temperature were obtained from the Iranian Meteorological Organization. Considering the climate change scenarios RCP4.5, RCP2.6 and RCP8.5 for the coming period 2010-2100 were evaluated under the canESM2 climate change model of Aharchai Basin. Due to the low accuracy of the general circulation models, the SDSM4.2 miniaturization model was used and the changes in precipitation and mean temperature parameters were simulated for future time periods. In this study, to calibrate the SDSM model, among the 26 large scale climate parameters (NCEP), on average, 3 parameters have the highest correlation with the mean temperature and 5 parameters have the highest correlation with the average precipitation in the Aharchai Basin. The results of climatic parameters prediction showed that simulation of climatic parameters mean temperature was performed with higher accuracy than mean precipitation values. The reason is that the precipitation data are not normal and unconditional. The results show that the basin temperature averaged more during the period 2070-2099 under the scenario RCP8.5 than the observations period of 1964-2005 and the basin precipitation during the period 2070-2099 under the scenario RCP2.6 showed the highest increase in the entire study period.
Miss Motahhareh Zargari, Dr Mahdi Boroughani, Dr Alireza Entezari, Dr Abbas Mofidi, Dr Mohammad Baaghideh,
Volume 24, Issue 72 (3-2024)
Abstract
The aim of the present study is to dynamically model the spatial-temporal characteristics of dust in the south and southeast of Iran with REG-CM4 model using monthly dust data and RegCM4 data. For this purpose, the dust distribution of the IDW method along with the dust diagrams were plotted. The RegCM4 model was implemented with the paired Lambert image imaging system for 40 km horizontal separation with the paired chemistry model. The location of monthly and annual dust distribution shows the highest amounts of dust for the cities of Zabol, Bandar Abbas, Zahedan and Jask compared to Sirjan, Kahnooj and Lar stations. The highest frequency of dust in Sistan and Baluchestan (48%), Hormozgan (27%) and Fars provinces with 16% and the lowest frequency for Kerman province (9%). In general, the summer seasons (at Sistan station) and the winter (Kerman station) have the highest and minimum dust events, respectively. The time survey also has the highest amount of dust for the warm months of the year and the lowest for the cold months of the year. July at Zabol station and November and December at Sirjan station have the highest and lowest dust levels, respectively. The RegCM4 climate model also shows maximum dust on the southeast, south and south coasts for different variables.
Mrs Maryam Sanaei, Dr Gholamreza Barati, Dr Alireza Shakiba,
Volume 24, Issue 72 (3-2024)
Abstract
Climate change, including spatial changes in rainfall following the increase in greenhouse gases, is a challenge that affects various aspects of life in human societies today. In this study, the long-term spatial changes of the rainy season from September to May were studied using the statistics of "local Moran" and "Hot spots of Getis Ord-J" during 5 5-year periods from 1991 to 2015. The application of local Moran statistics showed that areas with long rainfall periods are in good agreement with the countrychr('39')s rainfall pattern. This adaptation is accompanied by a negative spatial correlation in lands with short rainfall periods. The pattern obtained from the hot spot statistics also showed itself to be more consistent and corresponded to two very low rainfall regimes in the southeast and center, while according to local Moran statistics, this pattern was more scattered and parts of it had a low southern precipitation regime. . In addition, the results of Alexandersonchr('39')s statistics to identify mutations in the long-term series of the rainy season showed that the time series of 13 stations out of 108 stations studied experienced a sudden jump that these mutations are more in the southern stations in the country and in later years. It has occurred since 2000 AD.
Hadi Zerafati, Yousef Ghavidel, Manuchehr Farajzadeh,
Volume 24, Issue 72 (3-2024)
Abstract
In this study, for statistical studies to determine days whit temperature above 50°c, the reanalyzed data of the nineteenth, twentieth and twenty-first centuries for the West Asia region (12 to 42.5 degrees north latitude and 36 to 63.5 degrees east longitude) have been used. Also, for synoptic analysis of extreme temperatures, HGT, AIR, UWND, VWND and SLP data were used. To conduct this research, first, extreme temperature data above 50° during the last 185 years were extracted for the study area in the hot season (June, July, August and September). After identifying days whit above 50° c, HGT data at the level of 500 hp were extracted and WARD clustering was applied. Finally, after identifying the clusters, the days whit the highest temperature that occurred in each cluster were selected for synoptic analysis. It can be said that all altitude patterns of geopotential meters (HGT) at the level of 500 hp show that the main cause of occurrence and distribution of temperatures above 50°c in West Asia are high-altitude (high-pressure) subtropical West Asia, which due to the location of its high-pressure core on the Zagros and sometimes the Arabian Peninsula, it has been referred to as the Zagros or Saudi high-pressure in terms of interest and taste. What is certain, however, is the high-pressure independent identity of the subtropical Azores, which has been mentioned in numerous articles and is known to be the main cause of the heat in the West Asian region, especially Iran.
Mr Danesh Nasiri, Dr Reza Borna, Dr Manijeh Zohourian Pordel,
Volume 24, Issue 72 (3-2024)
Abstract
Knowledge of supernatural microphysical properties and revealing its relationship with the spatial temporal distribution of precipitation can significantly increase the accuracy of precipitation predictions. The main purpose of this study is to reveal the relationship between the Cloud microphysical structure and the distribution of precipitation in Khuzestan province. In this regard, first 3 inclusive rainfall events in Khuzestan province were selected and their 24-hour cumulative rainfall values were obtained. The rainfall event of 17December2006, was selected as a sample of heavy rainfall, 25 March 2019, as a medium rainfall case, and finally 27 October 2018, as a light rainfall case. Microphysical factors of clouds producing these precipitations were obtained from MODIS (MOD06) cloud product. These factors included temperature, pressure, and cloud top height, optical thickness, and cloud fraction. Finally, by generating a matrix with 64000 information codes, and performing spatial correlation analysis at a confidence level of 0.95, the relationship between the Cloud microphysical structure and the spatial values and distribution of selected precipitates was revealed. The results showed that in the case study of heavy and medium rainfall, the spatial average of 24-hour cumulative rainfall in the province was 36 and 12 mm, respectively. A fully developed cloud structure with a cloud ratio of more than 75% and a vertical expansion of 6 to 9 thousand meters, with an optical thickness of 40 to 50, has led to the occurrence of these widespread and significant rainfall in the province. While in the case of light rain, a significant discontinuation was seen in the horizontal expansion of the cloud cover in the province and the cloud cover percentage was less than 10%. In addition, the factors related to the vertical expansion of the cloud were much lower, so that the height of the cloud peak in this rainfall was between 3 to 5 thousand meters. The results of this study showed that in heavy and medium rainfall cases, a significant spatial correlation was observed at a confidence level of 0.95 between MOD06 Cloud microphysical factors and recorded precipitation values, while no significant spatial correlation was observed in light rainfall case.
Dr Behrouz Sobhani, Dr Mehdi Aalijahan,
Volume 24, Issue 73 (6-2024)
Abstract
Today, fine dust and dust storms have become one of the important issues and problems of Iran and other regions of the world. This study is conducted to identify synoptic patterns of the dust storms in Ardabil Province (Iran) and monitor the origin and pathway of its places. The studied period is 34 years (1979-2013). The data used in this work are from synoptic stations of Ardabil province and the NASA’s upper atmosphere database. To achieve the goals of the study, the Environment to Circulation, Hierarchical Clustering Methods, and HYSPLIT model were used. According to the results, three patterns of geopotential height at 500 hPa levels were identified. Pattern No. 1 and 2 are almost similar to each other and represent the occurrence of a deep trough that formed from Central Europe and extended to the middle of the Red Sea. Based on these patterns, the study area is located in the East of this trough. The third pattern represents the occurrence of cut-of-low pressure blocking over the Black Sea and adjacent areas and placement of Ardabil province in the East trough of the formed blocking. The origin of dust in patterns 1 and 2 is the Eastern regions of Iraq and West of Iran while in pattern 3 is at 500 hPa level of the central areas of Iraq and at pressure levels of 850 and 1000 hPa of the central regions of Syria.
Keywords: Dust storm, Pattern extraction, synoptic analyses, HYSPLIT model, Ardabil province
Mrs Somayeh Naderi, Prof. Bohloul Alijani, Prof. Zahra Hedjazizadeh, Dr. Hasan Heidari, Dr. Karim Abbaspour,
Volume 24, Issue 73 (6-2024)
Abstract
Evidence suggests that climate change will create uncertain regional agricultural production stability in the coming decades. This research investigated the impact of climate change on hydrology and sugar beet yield as one of the main crops in the Urmia lake basin using the Soil and Water Assessment Tool (SWAT). To address this, a baseline SWAT model was setup for 1986-2014. Afterward, the output was calibrated (1989-2004) and validated (2005-2014) in the SWAT-CUP software using the SUFI2 algorithm to simulate streamflow of 23 gauging stations and crop yield. The Nash-Sutcliffe efficiency was 0.43 and 0.53 for calibration and validation periods, sequentially. The Percent Bias was 45% and 16% for calibration and validation periods, respectively. As well as the agreement indices of 0.71 and the little Percent Bias (-6% to 10%) for crop production, verified the model's efficiency. The next step was downscaling and bias-correction of the precipitation and temperature data received from 3 climate models, namely GFDL, HadGEM2, and IPSL under RCP4.5 and RCP8.5 using CCT program. Then, the downscaled data were fed to SWAT, and Finally, hydrological fluxes and sugar beet yield were estimated for 2021-2050. Despite a dispersion of precipitation changes ranging from -12% to +35% in most scenarios, results highlight the pivotal role that the warmer temperature (+2.7°C) increases evaporation, resulting in sharpened pressure on water resources and runoff, especially, at the beginning of crop growth season. Finally, the negative impacts on crop productivity (-45%) is not unexpected. This means that sugar beet may suffer from climate change impacts, and the production of this plant will change over the next period in this region.
Keywords: Climate Change, Sugar Beet, Urmia Lake Basin, Sensitivity Analysis, SWAT.
Ms Akram Hedayati Dezfuli, Ms Zahra Ghassabi,
Volume 24, Issue 73 (6-2024)
Abstract
Flood is one of the most destructive natural phenomena. Every year it brings extensive losses to the country’s financial and human resources. In our country, major parts of Iran’s provinces are always at risk of flooding. The Gorgan and Atrak catchments have also become more important, as several floods have occurred in Golestan province in recent years, causing many deaths and economic losses. The purpose of this study was to investigate the synoptic and thermodynamic conditions of the March 2019 flood event in Golestan province in order to atmospheric system that lead to such floods. This study includes statistical analysis of provincial stations (Gorgan, Gonbadkavus, Aliabadkatol, Hashemabad, Kalale, Maravetape and Bandaretokman), calculating of the return period of precipitation during the available statistical period of each station, analysis of synoptic maps on the day of the flood event, the analysis of satellite images of the days involved in the flood, and calculation of instability indices of the Gorgans’s station. Statistical results showed that Gorgan and Gonbadkavus stations, with the highest amount of rainfall in March 2019, had a return period with 800 and 400 years respectively. Also the highest amount index of Gorgan with values of K=26°c, PW= 0.27 cm and TT= 48 was obtained with high relative humidity (about 80%). The analysis of the synoptic maps showed the severe sea level pressure and mid- level height drop with a deep trough in the study area, which led to extreme rainfall.
Key words: Flood, return period, Synoptic maps, instability indices, Golestan province.
Zoleikha Khezerluei Mohammadyar, , Bohloul Alijani,
Volume 24, Issue 73 (6-2024)
Abstract
The purpose of this article is to analyze the frequency and severity of the one to six days of rainfall in Iran. The trend of frequency changes and severity of each course was identified using my-candle test and the slope estimator during the 1968-1988 period. Then, using the main component analysis method and cluster analysis method, the entire stations were categorized in five clusters (abundance) and four (intensity) based on the annual changes of frequency indicators and intensity of precipitation. Cluster 1 and 2 stations represent the frequency of precipitation periods with a severe or without trend. The two clusters were mostly established in the southern half of Iran. Cluster 4 and 5 stations represent the frequency of precipitation periods with a positive (mild) trend, mainly in the northern part of the country. Cluster 3 stations represent the frequency of precipitation periods with decreased (mild) trends, which are mostly focused on west and southwestern Iran. The clustering results of the stations based on the intensity index of precipitation periods, contrary to many results; do not show a specific pattern. But in the cluster, there has been a severe decrease in the last half century. The stations of this cluster are mostly concentrated in the northern parts of the country. Other clusters are scattered in almost all parts of the country. Accordingly, it can be concluded that the frequency of precipitation periods in the northern latitudes of incremental processes (average or weak) and the severity of precipitation periods in these latitudes (north of the country) had severe declining trends.
Keywords: Frequency of precipitation, intensity of precipitation, analysis of main components, clustering, process.
Hossein Jahantigh, Esmail Rashidi, Abdolhossein Adel Zadeh,
Volume 24, Issue 73 (6-2024)
Abstract
Objectives: The purpose of this article, the relationship between maximum temperature of Kerman province geopotential height at 500 hPa to avoid risks and losses are extreme temperatures.
Method: In this paper, the approach has been used in the circulation to peripheral circulation patterns will be assessed based approach to environmental data. Therefore, we used two databases. First Base event database environment (surface). In this regard, the surface temperature is selected stations Kerman province. The maximum temperature of the stations in the period 01.01.1368 to 01.01.1398 for 30 years to 10957 the number of days were obtained from the meteorological province. Another database contains data that the data of geopotential height at 500 hPa
Dr Zahra Hejazizadeh, Dr Mehry Akbary, Zarin Jamshidiyini,
Volume 24, Issue 74 (9-2024)
Abstract
The present study investigated the impacts of NAO and ENSO on the precipitation in the southern shores of Caspian Sea. The accumulated monthly and annual rainfalls from 5 synoptic stations during the years (1956-2017) were taken through Islamic Republic of Iran Meteorology Organization (IRIMO) and the Multivariate Enso Indices (MEI) and NAO activity years are obtained from National Oceanic Atmospheric Administration. Pearson correlation was used to investigate the relationship between indices and precipitation amounts of selected stations. The results showed that there was a significant relationship between precipitation and NAO index in some months in all stations but this correlation was not following a particular pattern in all the stations. The maximum correlations were observed at Babolsar and Anzali station and the least correlation was found at Gorgan stations. The correlation between precipitation and different phases of NAO showed that there was a positive correlation between precipitation and negative phase of the index in Ramsar station and a negative correlation between precipitation and positive phase in the Gorgan station.The results of the Pearson correlation show a significant correlation between the MEI and rainfall amounts in the autumn in some stations in the early winter. In Review drought and wet periods with both Indicator it was observed that the behavior of the stations in the El Niño period, which was with different phases of the NAO was not entirely harmonious but the coefficient of 89% of rainfall in normal and more than normal during the period of El Niño showed that Elnino is better fitted to normal and more than normal rainfall in these stations also coefficient of 60% of weak to severe droughts in the Lanina period in the selected stations Indicates that the LaNina phase was more related with severe droughts in the under studied period.
Tooba Alizadeh, Majid Rezaei Banafsheh, Hashem Rostamzadeh, Gholamreza Goodarzi, Hedar Maleki, Hamzeh Alizadeh,
Volume 24, Issue 74 (9-2024)
Abstract
The aim of this study was to identify the epicenter and co-occurrence factors of dust storm wave from 1 to 3 November 2017 in Kermanshah. To investigate the synoptic conditions of the causes of this phenomenon, from the European Central Center (ESMWF) mid-term weather forecast data set with a resolution of 0.125 degrees of arc including, geopotential height, omega, sea level pressure, orbital and meridional components, humidity. The Lagrangian method of HYSPLIT model was used to orient the source of dust particles. in this study, dust storm WRF-chem was simulated using a paired numerical weather forecasting model. Finally, through the processing of MODIS satellite images, its scope was determined. Examination of HYSPLIT tracking maps shows that two general paths for dust transfer to the area can be identified. 1- The northwest-southeast route, which passes through dust cores formed in the deserts of Iraq and Syria, transports dust to the western half of Iran. 2- Southwest to west of Iran and Kermanshah, which is the main source of dust on November 2 and 3, The source of the particles is Kuwait, northern Saudi Arabia and part of Iraq. The spatial distribution of the dust interpreted by the MODIS sensor images is consistent with the spatial distribution of the dust concentration simulated by the WRF-chem model.
Maryam Aghaie, Siamak Dokhani, Ebrahim Omidvar,
Volume 24, Issue 74 (9-2024)
Abstract
Rain water harvesting is an appropriate option for storing surface runoff for subsequent uses during periods with limited access to water. The most important step in the application of rainwater harvesting systems (RWH) is the site selection suitable areas. Therefore, by identifying suitable sites for this purpose, time and cost will be saved . In this research, multivariate regression model and GIS were used to site selection in situ (RWH) in Tajare watershed. For this purpose, layers such as crown cover, litter, rock and stones, soil, curve number, rainfall, slope and depth of field as independent variable and infiltration were considered as the dependent variable. Then, according to the maps, their values were calculated in average for each of the 27 sub-basins. Also, to investigate the relationship between these variables and weighting, each of the effective layers of multi-variable regression was used by the stepwise method The results showed that the linear multivariate regression model with an explanation coefficient of 0.993 was able to estimate the penetration factor values well In terms of grade of importance, the curve number variables with a coefficient of -2.433, depth of soil with a coefficient of 0.3488, and rubble and gravel percent with a coefficient of 0.057, were the most important, and other factors were not significant. Comparison of the map from the site selection of multivariate regression in this research with some recommended criteria of various research studies showed that the predicted classes with good in the central parts of the basin and very good in the upstream areas of the basin which in the eastern and southeastern part of the basin fit have a good overlap with the recommended areas with these criteria.
Dana Rahimi, Javad Khoshhal Dastjerdi, Dariush Rahimi,
Volume 24, Issue 74 (9-2024)
Abstract
Among natural disasters, floods have the highest human toll. The economic impacts of floods are greater in developing countries, including Iran, and are particularly severe in the colder months of the year in the west of the country. The purpose of the present study is to analyze the most severe historical synoptic floods that occurred in Karkheh Basin (1 April, 2019). Descriptive - analytical research method and its environmental approach into circulation. Analysis of synoptic systems of large floods such as the April 12, 2019 floods show that Western Europe's high-pressure systems, Black sea, East of the Caspian and low pressure north of the Red Sea, Eastern Mediterranean in harmony with the high-rise systems of Western Europe, Low Mediterranean East with a temperature drop of about 50 degrees Celsius(The temperature at sea level In the eastern Mediterranean and Red Sea about 25 degrees Celsius and in the middle of the atmosphere -25 degrees Celsius) also the climb Humidity from the Arabian Sea, North Indian Ocean, Red Sea, Oman Sea and Persian Gulf and Along with Mid-width cold air loss On the area and the establishment of the Polar jet stream) Core up to 70 m(And the establishment of the front jet stream And positive rotation area On the area shows the structure of the synoptic systems causing the flood in the area.
Mrs Mahnaz Saber, Dr Bromand Salahi, Dr Abbas Mofidi,
Volume 24, Issue 74 (9-2024)
Abstract
In this study, the spatiotemporal variations of evapotranspiration (ET) were investigated in the southern part of the Aras River catchment. For this purpose, the ET networked data of FLDAS Noah model with horizontal resolution of 0.1 * 0.1 degree were used for a period of 38 years (2019-1982). After validating the data, the average annual ET values for the region were determined first. Then the monthly and seasonal distribution of the parameter were analyzed spatially. Subsequently, ET variations and anomalies were evaluated year to year. Also, the spatial distribution of the occurrence frequency of ET was investigated by considering the absolute thresholds of 50, 80, 100 and 120 mm for the Aras basin. The results show that the annual ET in the east of the basin is higher than the west of the basin. In the seasonal scale, spring and summer have the highest ET values, respectively. In the monthly scale, Mayو June, April and March had the highest ET values, respectively. In contrast, the autumn and winter months have the lowest average ET values. Also, the whole basin during the study period has experienced three distinct periods of ET changes that in the eastern and western parts of the basin, despite the same behavior in the second and third periods, a significant difference was observed in the first period. The results also indicate the existence of positive anomalies after 2002 in the whole basin, the highest values occurred in 2018 in the west of the basin. The study of the frequency of occurrence of absolute ET thresholds on the basin shows the high frequency of ET occurrence at all thresholds in the east of the basin. A study of nearly 4 decades of ET values in the Aras River Basin shows an increase in ET values over the last two decades over the entire basin, which can be attributed to the occurrence of global warming.