Showing 23 results for Spi
, ,
Volume 9, Issue 7 (5-2009)
Abstract
Behroz Sobhani, Ata Gafarigilandeh, Akbar Goldost,
Volume 15, Issue 36 (6-2015)
Abstract
Drought defined as a climatic phenomenon with the humidity and rainfall shortage as compared with normal conditions. This phenomenon affects on all of aspects of human activities, severely. while, studies associated with this phenomenon on the basis of appropriate methods are very low. In the present study, effort has been made to analyze the drought state in Ardabil province by means of software system capabilities in MATLAB and SEPI index in two temporal scales of 6 and 12 months. The climatic data of synoptically stations of Ardabil were used, Parsabad and khalkhal countian in Ardabil province. Results of study show that SEPI index reflects the features of two SPI and SEI indices well. And also enters temperature in the studying of drought conditions as one of the effective parameters in changing of drought intensity. Therefore, the investigation into drought with SEPI index is better than SPI index. Studies associated to drought on the basis of SEPI index shows that drought process is increasing in Ardabil province. Temperature also has an increasing flow with higher intensity. Longest temporal continuation of drought in province, has occurred in Parsabad station in temporal scale of 12 months, from June, 1998 to November, 1999 in 18 month period. The greatest percentage of drought occurrence is in Parsabad station and the minimum of that is observed in Khalkhal station.
[1] - Akbar Goldust: PhD student's of climatology in environmental planning Mohaggeg Ardabil University
Mostafa Karimi, Ghasem Azizi, Aliakbar Shamsipour, Lila Rezaee Mahdi,
Volume 16, Issue 41 (6-2016)
Abstract
In this study is simulation of role of topography in thickness and Inland penetration of sea-breeze in southern coast of the Caspian Sea. The RegCM4 as a regional scale climate model coupled with a lake model and also the reanalysis data of NCEP / NCAR used to determine of the initial conditions of the model. The model was run during the peak of sea breeze on the southern coast of the Caspian Sea (July 2002) in both conditions (with mountains) and (without mountains). the outputs indicated that in without topography condition depth of the sea breeze will increase to the current position the southern slopes of the Alborz Mountains ( latitude ᵒ35 ) but the land breeze in the area is gone. The maximum speed and changes in wind direction observed on the coast southeast and central Alborz respectively. In addition with non-topography conditions, the thickness of sea breeze in different areas significantly has increased with the highest rate on the eastern coast (longitude ᵒ53).
Mohammad Saligheh, Mohammad Hossein Nasserzadeh, Thmineh Chehreara Ziabari,
Volume 16, Issue 43 (12-2016)
Abstract
In this research, the relationship between NCPI and CACO indices with autumn precipitation of Southern Coast of Caspian Sea (SCCS) was investigated. In this regard, two sets of data were used (Aphrodite and Station). And the days with more rainfall than long-term average rainfall station and on condition that the rainfall is more than 70% of the region rainfall, were chosen as a day of widespread rainfall. The sea level pressure data was extracted and by cluster analysis and coalition method was clustered. Then, a representative of the widespread precipitation days from station dataset was selected, investigated and analyzed accordingly. The results state that within all patterns there exists a high pressure on the upper side of the Caspian Sea, or a margin of high pressure is extended on to the sea itself. These high pressure regions have relatively cold nature that can cause currents in the northern direction while intersecting with the relatively warm water during the summer. These currents can absorb moisture during their motion towards south which can lead to their instability. In addition, one should not forget the fact that in each three investigated patterns, dynamic factors at high levels have intensified the abovementioned phenomenon and enhanced the instability, which as a result brought about widespread precipitation. Continuously, the abovementioned Remote bond indices were extracted on a daily basis and their relation to north coast widespread rainfalls was studied, which came to a meaningful relationship between these index sets and fall index sets. The relationship is direct with NCPI or surveyed stations, and it’s an inverse relationship with CACO. On the other hand, the study of indexes anomalies on the days without rainfall and with rainfall was done by One Way ANOVA and Tukey test. The result was a meaningful index anomaly on the days with and without rainfall.
Alimohammad Khorshiddoust, Behrooz Sarraf, Bagher Ghermez Cheshmeh, Mrs Fatemeh Jafarzadeh,
Volume 17, Issue 47 (12-2017)
Abstract
In recent years, the severe fluctuations in precipitation have affected various parts of the country. On the southern coasts of the Caspian Sea, precipitation as one of the important climatic parameters has undergone changes due to global climate change. In the present study, we tried to evaluate the effect of climate change on rainfall in this region by applying a suitable model. In this study, observational period rainfall (1961-2001) was analyzed. the output of the HadCM3 model was used. At first, seven synoptic stations were selected and their data were analyzed in terms of accuracy, and length of statistical period, and lost data was restored. The AOGCM data were simulated using the SDSM model and the rainfall values were simulated for the observation period. After confirming the matching of the simulated data with observational data, the values of the Future (2039-2011) is estimated. The estimation errors of the SDSM model were calculated monthly by MBE and MAE criteria, and then compared. The output of the SDSM model was used to study the total annual precipitation in days with rainfall of more than 1 mm in the observation period and the upcoming period (2011-2039) by the R-Climdex model and the values of the PRCPTOT index Became zoning in the Future. The results showed that the model error in season with high rainfall is more than seasons with low rainfall. On a monthly scale, the maximum error occurred in the months of September, October, November and December. The maximum error in the fall and the minimum error was calculated in the spring and April and May months. According to the results, the total annual rainfall in the period of 2039-2011 will decrease in Anzali, Babolsar, Gorgan and Noshahr stations and rainfall will increase in stations of Astara, Ramsar and Rasht. Geographical distribution of selected were 5 sites in the Khuzestan, 20 sites in Bushehr, 24 sites in Hormozghan and 12 sites in Sistan and Baluchistan provinces. In total, 9000 sites were selected with a 2 km2 were suitable for large scale microalgae cultivation. The total area of these sites were estimated to be 18000 km2. The highest number of proper sites were found in Hormozghan province and lowest numbers of sites were found in Khuzestan province. The availability of technical service, carbon dioxide point resources from oil and gas units are an advantages for microalgae related activities in the Bushehr and Khuzestan provinces. The higher quality of water in the Sistan and Baluchistan province is an advantages for development of microalgae biomass production in the area.
nk href="moz-extension://8b922523-7922-435a-ac74-8ddb59e9beaf/skin/s3gt_tooltip_mini.css" rel="stylesheet" type="text/css" >
nk href="moz-extension://8b922523-7922-435a-ac74-8ddb59e9beaf/skin/s3gt_tooltip_mini.css" rel="stylesheet" type="text/css" >
Farzaneh Sasanpour, Sara Alizadeh, Hourieh Aarabi Moghadam,
Volume 18, Issue 48 (3-2018)
Abstract
Livability approach is defined as the healthy, safe, suitable and economically accessible urban system that brings about high life quality and is considered as a subset of sustainable development. Although investigating urban livability can be advantageous in identifying deficiencies and taking actions in order to improve livability of the living environment of residents, but unfortunately there has been inadequate considerations about livability theory in Iran. the result, in this study, the livability of Urumia city has been investigated. Firstly, after devising 24 factors in 4 aspects (Physical-Environmental, Economic, Social and Health) this index was evaluated in urban areas by using newly invented model RALSPI with descriptive-analytical approach. Finally, based on this model, the areas were placed within the range of very livable to intolerable, so that District #1 was determined as the best area with livability score of 0.31 and District #2 was determined as the most unlivable area with the score of 0.007. This issue revealed a huge gap between the areas of the city.
Ali Ahmadabadi, Zahra Sedighifar,
Volume 18, Issue 51 (6-2018)
Abstract
Climate change is one of the most important challenges that has affected various parts of human life on Earth. In the present study, in order to investigate the climate change, three synoptic stations of Karaj, Mehrabad and Dashan Tepeh with the help of the statistical statistic downscaling model (SDSM) model were used to predict the statistical period of 2016-2045. Finally, the effects of climate change on the hydrologic conditions of the basin with the help of the model (SWAT) was simulated by the Soil and Water Assessment Tool. The amount of surface runoff and runoff at the study area is 10.59 mm in the studied observation period, but this rate was estimated to be 21.27 mm for the predicted period due to the increase of urbanization and changes in utilization. The results of the research, while highlighting the importance of the effects of climate change, are necessary for their application in applying proper management to adapt to climate change in the future policies of the basin management.
Mrs Masooume Darmani, Mohammad Nohtani, Haydeh Ara, Ali Golkarian, Salman Sharif Azari,
Volume 18, Issue 51 (6-2018)
Abstract
One of the most important processes of erosion and sediment transport in streams is the river most complex engineering issues.this process special effects on water quality indices, action suburbs floor and destroyed much damage to the river and also into the development plans Lack of continuity sediment sampling and measurement of many existing stations. due to the low number of hydrometric stations in Iran and the lack of continuity of sediment sampling and measuring in many existing stations, on one hand the exact amount of sediment load in many rivers in the country is not available and because of differences in climatic, hydrological and topographical conditions in the country, on the other hand, the preparation and calibration of sediment Erosion Models different regions, is unavoidableCalibration models of erosion and sedimentation in different locations is difficult and requires financial capital andthe time . the But evolutionary optimization algorithm able to resolve this problems of mathematical and experimental methods in this paper, a new optimization algorithm spiders can be made to education And the evolutionary pattern for input (discharge and precipitation) and rain-gauge gauging stations and Watershed Kardeh designated evolutionary algorithms and artificial network performance for 24 year 24-year dam catchment Kardeh for the period studied. In conclusion, the results proved that social spiders optimization algorithm t better resultspredic to for sediment in watershed Kardeh
Shadieh Heydari Tasheh Kaboud, Younes Khoshkhoo,
Volume 19, Issue 53 (6-2019)
Abstract
The aim of this research is the study of the climate change impacts on the seasonal and annual reference evapotranspiration time scales in some selected stations located in the West of Iran. To this purpose, four stations including Sanandaj, Saghez, Khorramabad and Kermanshah synoptic stations with enough long-term data were selected and the climate change impact on the reference evapotranspiration of these stations under two RCP2.6 and RCP8.5 scenarios in three future time periods including 2011-2040, 2041-2070 and 2071-2100 in comparison with the 1970-1999 base period was studied. The FAO-Penman-Montieth method was applied to calculating reference evapotranspiration and the CanESM2 general circulation model and SDSM downscaling method were used to simulating future climate conditions under the climatic scenarios. The results showed that the mean reference evapotranspiration in the annual and autumn and winter time scales in comparison to the base period will significantly increase for all of the studied stations under all of the scenarios and periods at the 0.01 confidence level. For spring season, the only significant change of the future period mean reference evapotranspiration compared to the base period in the all of the studied area will be a significant increase at the 0.01 confidence level in the 2071-2100 period under the RCP8.5 scenario and for the summer season, this significant increasing rate will occur in the 2041-2070 and 2071-2100 periods under the RCP8.5 scenario. The overall results of this research showed that the highest increasing rate of the future periods in comparison with the base period for all of the seasonal and annual time periods and for all of the studied area will under RCP8.5 scenario and in the 2071-2100 time periods. by comparing the reference evapotranspiration change rates between the different seasonal and annual scales, the results showed that the increasing rate of the mean reference evapotranspiration at the West of Iran will be very remarkably in the autumn and winter seasons compared to the other time scales.
Msc. Graduated Student Najmeh Daneshvar-Marvast, Dr Somayeh Soltani-Gerdefaramarzi, Dr Samaneh Poormohammadi,
Volume 19, Issue 55 (12-2019)
Abstract
The phenomenon of evapotranspiration causes water and moisture losses from water, soil and vegetation levels. Due to the small amount of atmospheric precipitation and water resource constraints in Iran, it is important to calculate it through a suitable method. The present research attempts to evaluate the evapotranspiration reference crop (ETo) and present it in the form of zoning map as a basic tool for water management. In this study, the long-term average of seven meteorological stations and evaporation pan data were used to determine the appropriate ETo estimation method. Evapotranspiration of reference crop was calculated to 14 methods the based on climatic information in each station. Computational methods including combinational methods Penman-based, radiation-temperature method, temperature method and radiation method. The most appropriate computational method was selected based on the R2 and Nash -Sutcliffe statistics. The zoning of evapotranspiration of reference crop was carried out based on the geographic information of the meteorological stations and the GIS software. The results of the research indicate that the best method for this region as the cold and moderate climate are FAO radiation and Blaney-Criddle. Also, the zoning result shows that west of the catchment has less evapotranspiration rather than its east. Sunshine hours, maximum temperature and wind speed were the most effective factors for evapotranspiration in this area by sensitivity analysis.
Mehdi Asadi, Mokhtar Karami,
Volume 20, Issue 56 (3-2020)
Abstract
The purpose of this study is to determine the evapotranspiration in Fars province that in many studies such as hydrological balance of water, irrigation systems design and management, simulation of product volume and management of water resources is very important. To do this, first, required data such as daily temperature, humidity, precipitation, wind speed, solar radiation pressures, solar radiation, etc. was collected. We used 12 stations with the same statistical interval, for the period 1995-2015. In order to estimate the evapotranspiration of the reference plant in different growth stages, Torent White, Penman-Monteith and Hargreaves-Samani methods were used. Results showed that with decreasing latitude, the evapotranspiration rate increased, and the highest rate of evapotranspiration occurs in the south, southeast and the center of the study area. The correlation coefficient R2 between height and White Penman, Monteith and Hargreaves Samani, are 0.9135, 0.53223 and 0.5286 respectively.
Dr Yagob Dinpashoh, Miss Masoumeh Foroughi,
Volume 20, Issue 58 (9-2020)
Abstract
Reference evapotranspiration (ET0) is a climatic parameter and can be computed from weather data. It is one of the most important hydrological parameters for calculating crop water demand, scheduling irrigation systems, preparing input data to hydrological water-balance models, regional water resources assessment, and planning and management for a region and/or a basin. The climatic data from synoptic stations with more than 20 years continues record in West Azarbaijan province was used. The well-known FAO-PM56 method was used to calculate the ET0. Then Multiple linear Regression (MLR) was used to estimate the ET0. The RMSE, MEA, NSH, and R2 were used to evaluate the performance of the MLR model. Then, the correlation coefficient (r) between ET0 and each of the meteorological parameters was obtained. And finally, with using Path analysis method, the influence of direct (P) and indirect effects of the meteorological parameters on ET0 was calculated. In the studied synoptic stations, NSH between 0.91 and 0.99, R2 between 0.91 and 0.99, RMSE between 0.05 and 0.15, and MEA between 0.04 and 0.12 were obtained. Also, it was found that the wind speed at all of stations had a significant correlation (at the 0.01% level) with ET0. The path analysis results showed that the maximum value of P (direct effect of meteorological parameters on ET0) in all of the stations belongs to wind speed. The P value of wind speed in Urmia equal to 0.85, Piranshahr equal to 0.99, Takab equal to 0.97, Khoy equal to 0.90, Sardasht equal to 1.06, and Mahabad equal to 0.78 are obtained.
Farzaneh Madani, Afson Mahdavi, Mojtaba Rafiyan, Fatemeh Mohammad Niae Qaraee,
Volume 21, Issue 63 (12-2021)
Abstract
Spiritual-led urbanism is being structured as a new paradigm in urban planning. Social inequality, polarization, moral poverty, and a high prevalence of psychiatric disease are only part of the manifestation of the lack of attention to the issue of spirituality in the production of space. Indeed, the challenge of the contemporary city is the emergence of the process of personalization of space production and capitalization resulting from the dominance of the speculative model and its confrontation with identity and semantic structure. In contrast to these challenges, the discussion of spirituality in recent decades by prominent Harvard scholars has emerged as an interdisciplinary paradigm, embedded in a powerful stream of critical communication planning theory and requiring context. Therefore, the present article analyzes the theoretical field of research related to the paradigm of spiritual development in the production of urban space. This article is based on a combination and is meta synthesis. The statistical population of the study consists of 55 ISI and scientific-research articles in the period 2008-2019. In order to collect and data analyze, methods such as systematic review and open coding have been used. In this context, comprehensive form for summarizing and extracting data from selected research was developed which issues concerning public profile and the theoretical framework of the research. The research findings are presented in two parts: structural and content. The first section examines the general features of selected research, the unreliability of studies on the impact of spirituality on urban space production, and the second section elaborates on the theoretical framework of research on spatial spirituality. production of spiritual-
Dr Hossein Asakereh, Nasrin Varnaseri Ghandali,
Volume 22, Issue 64 (3-2022)
Abstract
Change in precipitation features is one of climate change outcome. Change in precipitation amount, especially in warm season, may influences climato-environmental phenomenon as well as human activity. In current research the decadal changes of monthly precipitation over the Caspian coast of Iran territory was evaluated. Accordingly, a large number of rain gauge stations (385 stations), where rainfall is measured painstakingly, have been used. these stations are under the supervision of Meteorological Organization of the country and Ministry of Energy. Since the original dataset pertaining to the precipitation prior to 1966 had noticeable missing values, and the data after 2016 were not accessible, a continuous time period from January 1966 to December 2016 was selected. From the daily precipitation of aforementioned stations contour maps were created using an ordinary Kriging method. The spatial resolution of these precipitation maps was 3 km * 3 km. Our finding showed that during the under investigation period the maximum gradient of precipitation moved from coastal parts toward mountainous area. Decrease in the area with high precipitation and increase in the low precipitation area is an other prominent decadal characteristics. According to the previous study, these changes might attributed to changes in systems which effect precipitation in the Caspian coast of Iran (northward movement in polar vortex, sub-tropical high pressure and cyclone truck). In addition, increasing temperature trends in the summer tend to decrease temperature spatial differences. Therefore, the convectional precipitation during summer has been decreased.
Associated Professor Hooshmand Ataei, Mrs Mahsa Ravarian, Mr Seyed Alireza Tashakori Hashemi,
Volume 23, Issue 69 (6-2023)
Abstract
So far, several models have been proposed for estimating different climate parameters, but due to the lack of valid and long-term data in some meteorological stations, some models have been difficult to use. The SIMETAV V.1.0 model has been developed in cooperation with the University of California Davis and the Water Resources Authority of California in 2005. The SIMETAW model is a new and innovative tool for the estimation of applied water evapotranspiration (ETAW). SIMETAW simulation model is presented to estimate potential evapotranspiration and also estimate the net amount of water required for irrigation (ETaw). In addition, using this model, you can simulate daily meteorological data from meteorological data. The simulation of daily weather information where there are only monthly averages is a great tool for filling out lost data. In this research, Simetaw simulation model predicts different climate parameters such as solar radiation, minimum and maximum temperature, wind speed, dew point, precipitation and evapotranspiration potential in four different semi-arid climate zones (Mashhad). Dry (Bandar Abbas), moderate and humid (Ramsar) and Mediterranean (Sanandaj) during the years (1967-2017). The results of these studies showed that SIMETAW model has high ability to simulate climate variables and has the highest model accuracy in precipitation simulation (R2 = 0.998) and maximum temperature (R2 = 0.997) for semi-arid climate (Mashhad) , Dew point (R2 = 0.998) for temperate and humid climate (Ramsar), for radiation (R2 = 0.998) and wind speed (R2 = 0.9) for Mediterranean climate (Sanandaj) and minimum temperature (R2 = 0.998) for warm and dry climates (Bandar Abbas).
According to the sensitivity analysis of SIMETAW model, the input parameters of the model are respectively their effect on potential evapotranspiration from maximum temperature, precipitation, dew point temperature and minimum temperature, solar radiation and wind speed.
- Minoo Ahmadyan, - Bahroz Sobhani, - Sobhani@uma.ac.ir Jahanbakhsh Asl,
Volume 23, Issue 70 (9-2023)
Abstract
The evapotranspiration of the reference Crop is of particular importance due to the changes in climate parameters of temperature, sunlight, humidity and wind speed in combination. the purpose of this study is to investigate the effects of climate change on evapotranspiration of apple during the growing season.For this purpose, the ECMWF database has been used for observation data of Semirom and Urmia stations during 20-year period (1996-2001).To check this quantity in the next 20 years, the daily Downscaling dynamic data of the CORDEX project with a precision of 44% * 44% for the output of the ICHEC-EC-EARTH model under the two lines of 4.5 and 8.5 (RCP) was used for the period (2017-2037). In order to reduce the errors in the model estimates, the post-processing action of the estimated events was fulfilled. Then, minimum temperature data, maximum temperature, relative humidity, wind speed and radiation, potential evapotranspiration have been calculated using Penman- Monteith FAO method, which is more accurate than other models, and using the non-parametric Man-Kendall test and the Sen’s Slope estimator nonparametric Method in the confidence range, 95% evapotranspiration was determined. The results showed that evapotranspiration in both stations is increasing during the growing season. The ETo increase in the growth season of the apple tree stations was predicted from the base period for the trajectory of 4.5 and 8.5 for the Semirom 4.14.7 and 7.99.7, respectively, and for Orumiye Station, 26.5 and 11.8, respectively
Sanam Afaridi, Fereshte Ahmadi, Ali Soltani, Mahmood Mohamdi,
Volume 24, Issue 73 (6-2024)
Abstract
Optimal condition of accessibility and rapid, easy, and safe travel to health_ treatment land uses can be performed by the systematic analysis of transportation sub-systems like behavior. Developed countries are in essential need of proper transportation system for better accessibility. This paper aims to develop model, considering mode chains as well as the individual characters. This study benefits the analytic and quantitative research methods in developing mode choice model to evaluate the movement pattern of travel to health care centers in Shiraz central district (district 1). Each mode is the dependent variable whereas the socioeconomic characters are the independent variables. Filled questionnaire and geographical information system is used in collecting data. To generate the model, multinomial logit model was used that shows public transport like metro and bus are not the popular modes in access to hospitals. Movement pattern cognition in accessibility to special urban land uses, has an efficient role in urban policies and planning, which can be generalized and indigenize to healthcare travel behavior in other geographical areas. Results show that car ownership will increased the private car travel rate 8 times according to beta coefficient.. Taxi is the mode which is used in all three travels. People with lowest range of income and education use bus as their mode. Besides metro travel also has significant relation with low level of income and increase the travel rate 9 times.
Keywords: logit Model, Hospital, vehicle, travel mode, Shiraz City.
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.
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.
Shamsallah Asgari, Tayeb Razi, Mohamadreza Jafari, Ali Akbar Noroozi,
Volume 25, Issue 76 (3-2025)
Abstract
Due to the significance of forests in both the natural and human environment, this study aims to investigate the impact of meteorological drought on oak forest dieback in Ilam province. Specifically, the study seeks to determine the relationship between Zagros Forest drought and droughts in this particular region. The analysis utilizes the Standard Precipitation Index (SPI) to identify the frequency of droughts during different time periods. The results indicate that the years 2007, 2008, 2011, 2015, and 2016 experienced the highest occurrence of droughts. Additionally, remote sensing data from MODIS images were employed to examine the trend in tree greenness (NDVI) from 2000 to 2016. The analysis reveals a significant correlation (R2 = 0.9999) between the greenness trend and the drought index (SPI). Moreover, a land survey of oak drying points and simulation using Landsat satellite images, with a 15×15 pixel output from GIS software, indicate that approximately 17,894 hectares of forests in the region experienced drying and destruction between 2000 and 2016. By combining the oak forest drying layer with the output layers derived from drought zoning, visual indicators were created, and statistical analysis was conducted for three 5-year time series. The results demonstrate a correlation coefficient of 96.6% and an explanation coefficient of R2 = 0.985 for the 2002-2006 time series, a correlation coefficient of 95.4% and an explanation coefficient of R2 = 0.980 for the 2007-2011 time series, and a correlation coefficient of 98.8% and an explanation coefficient of R2 = 0.995 for the 2012-2016 time series. These findings illustrate the influence of drought and its variations in terms of intensity and duration on oak forests in the Zagros region of Ilam. Based on the study results, it is predicted that if the drought persists with the same trend, approximately 1,118.4 hectares of oak forests in Ilam province will dry up and be destroyed annually.
