Hamidreza Moradieraghi; abbas ali vali; fatemeh panahi; aliakbar davudirad
Volume 29, Issue 3 , October 2022, , Pages 211-220
Meisam Aramesh; abbas ali vali; Abolfazl Ranjbar
Volume 29, Issue 2 , July 2022, , Pages 146-160
Abstract
Desertification is a serious ecological, environmental, and socio-economic threat to the world, and there is a pressing need to develop a reasonable and reproducible method to assess it at different scales. Therefore, in the present paper, changes in cover and desertification of Kashan, Aran and Bidgol ...
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Desertification is a serious ecological, environmental, and socio-economic threat to the world, and there is a pressing need to develop a reasonable and reproducible method to assess it at different scales. Therefore, in the present paper, changes in cover and desertification of Kashan, Aran and Bidgol regions in the north of Isfahan were developed using Landsat ETM and OLI data. According to this research, NDVI (Normalized Difference Vegetation Index), TGSI (Topsoil Grain Size Index), and land surface albedo were selected as indicators for representing land surface conditions from vegetation biomass, landscape pattern, and reflection. A Decision Tree (DT) approach was used to assess the land cover change and desertification of the study area from 1995-2020. Temporal changes indicated an increase in NDVI, TGSI, and albedo trends during this period. The spatial distribution of NDVI showed that values greater than 0.5 were observed only in a small part of the west and southwest, while high values of TGSI and albedo occupied a large area of the study area. There was also a correlation between the above three indicators at 95% (R = 0.99). The results also showed that desertification is increasing in the study area, so that the intensity of desertification from 1995 to 2020 in classes without desertification was low, medium, and severe. The high desertification class decreased by 1420.75 square kilometers (13.54%), while severe desertification increased by approximately 1388.8 square kilometers (13.23%). The highest NDVI values were found in the non-desert area and the low desertification class, while the highest TGSI and albedo values were found in the high and severe desertification classes.
Tayebeh Sadat Sohrabi; Abolfazl Ranjbar Fordoie; Abbasali Vali; Seyed Hojat Mousavi
Volume 26, Issue 3 , September 2019, , Pages 689-703
Abstract
Iran is frequently exposed to local and synoptically dust storm due to the geographical location of Iran. In recent years, dust storm frequencies and intensities have been increased significantly in Iran and especially in Isfahan Province, seriously disrupting human life and affecting the quality of ...
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Iran is frequently exposed to local and synoptically dust storm due to the geographical location of Iran. In recent years, dust storm frequencies and intensities have been increased significantly in Iran and especially in Isfahan Province, seriously disrupting human life and affecting the quality of life. This phenomenon is particularly increased in the spring and summer. Climate factors play an important role in dust storms. In this research, spatiotemporal changes of climate factors and dust storms were studied. Therefore, we analyzed climate factors (precipitation, temperature, wind speed and humidity) and dust storms frequency during 1992 to 2016. Poisson regression model was used for statistical modeling of temporal and spatial variations of dust and climatic parameters. According to the models, there was conformity between the results and the predicted values throughout the months. In addition, the results showed that wind speed played a major role in the occurrence of dust storms and had the highest coefficient. The results also showed that most of the dusty days are in the spring and then in the eastern part of the province, which is related to the local centers in the eastern part of the province and summer winds.
Mohammad Sadegh Kahkhakohan; Abolfazl Rajbar Fordoie; Seyed Hojat Mousavi; Abbasali vali
Volume 26, Issue 3 , September 2019, , Pages 754-771
Abstract
Drought and its effects is one of the world's major concerns. As one of the countries in the dry belt of the earth, Iran has always been and is facing environmental issues and natural hazards caused by drought. Therefore, this study aimed to monitor the aridity in Sistan and Baluchestan using remote ...
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Drought and its effects is one of the world's major concerns. As one of the countries in the dry belt of the earth, Iran has always been and is facing environmental issues and natural hazards caused by drought. Therefore, this study aimed to monitor the aridity in Sistan and Baluchestan using remote sensing data and geographic information system techniques for over a period of 15 years (2015-2000). In this regard, the MODIS satellite images from 2000 to 2015 were analyzed by applying the yearly Precipitation Condition Index (PCI) and Standardized Precipitation Index (SPI). Then, the drought changes were evaluated using supervised classification method and difference images. The results showed that the years 2007 and 2001 with an area of 157383.06 and 306.05 km2 had the highest and lowest levels of precipitation, and also with an area of 49511.1 and 69233.83 km2 had the minimum and maximum level of drought, respectively. The most severity change of drought has been in time for the 2002-2001 period and the place also belong to parts of Khash, Iranshahr and Sarbaz who takes 194302.93 km2 of the province. Finally, the general trend of changes in precipitation and drought is decreasing and increasing, respectively, requiring the major planning of resources conservation and risk and crisis management to rehabilitate and maintain the ecosystem of arid regions.
zohre ebrahimi; abasali vali; mohammad khosroshahi; reza ghazavi
Volume 24, Issue 1 , May 2017, , Pages 152-164
Abstract
Wetlands in the central Iran lakes are considered as part of desert ecosystems and their destruction leads to adverse consequences. In central part of Iran, climatic and human factors have created significant differences between dry and wet surfaces of Gavkhooni wetland in recent decades, leading to ...
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Wetlands in the central Iran lakes are considered as part of desert ecosystems and their destruction leads to adverse consequences. In central part of Iran, climatic and human factors have created significant differences between dry and wet surfaces of Gavkhooni wetland in recent decades, leading to produce more dust in central part of Iran. The aim of this research was to assess the impact of dried bed of Gavkhooni wetland on the production of the internal dust in Isfahan province by using remote sensing and storm roses in the period of 22 years (1991- 1992 to 2011-2012). For this propose, the landsat imagery and anemometer data were used. After geometric and radiometric corrections, Normalized Difference Water Index (NDWI) was calculated and the dry and wet surfaces were separated. To determine wind erosion threshold velocity, undisturbed soil samples were transferred to the wind erosion meter. Then, the number of dusty days in the synoptic station of Isfahan was calculated based on the wind speed greater than wind threshold speed. Relationship between the number of dusty days and dried bed of wetland was evaluated with correlation analysis. Finally, to determine the dusty wind direction from the side of Gavkhuni wetland to Isfahan station, annual and seasonal wind roses and storm roses were plotted and evaluated. The results of this study based on the artificial neural network model showed that the most important factors influencing the bed of the Gavkhuni wetland were input flow rate, evaporation, drop in groundwater level, temperature, and rainfall, respectively. The results of the correlation analysis showed that there was a significant inverse relationship between the number of dusty days and dried bed of wetland in the seasons of autumn, spring, summer and annual scale in Isfahan station. Also, results of storm roses showed that dusty winds did not blow from wetland toward this station.
seyed hojat Mousavi; Abasali vali; Abolfazl Ranjbar Fordoye
Volume 23, Issue 3 , January 2017, , Pages 499-515
Abstract
Desertification is defined as rapid change in vegetation cover, plant community composition, hydrologic conditions, soil properties, or climate conditions, which results in an overall loss of ecosystem services and poses serious threats to sustainable livelihoods. The process represents one of the most ...
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Desertification is defined as rapid change in vegetation cover, plant community composition, hydrologic conditions, soil properties, or climate conditions, which results in an overall loss of ecosystem services and poses serious threats to sustainable livelihoods. The process represents one of the most threatening environmental hazards due to the large amount of people and land at risk. Therefore, this research was aimed to modeling of desertification and zonation of Haj Ali Gholi Playa according to the climate parameters such as temperature, rainfall amount, evapotranspiration potential, number of sunny hours, climate condition, drought (aridity), and maximum prevailing wind speed, using GIS technique and statistical methods. The modeling was performed using stepwise multiple regression analysis. According to the results, maximum significant relationship was found among desertification classes and dry zone with a determination coefficient of 0.999 and STD error of estimate of 0.033 (α ≥ 0.01). Other results are included the zonation map of desertification in the study area from very high zone to no-desertification zone, so that, the very high desertification zone is included about 679.75 km2 (%92.66) of present land degradation and has the possibility of increasing up to 5668.11 km2. In addition, the high desertification zone, covering about 5.22 km2 (%0.44) of present land degradation, can develop to 933.86 km2. The obtained results from validation test of the model show the descending trend of accuracy assessment index from the very high desertification zone to the no-desertification zone, indicating the necessary accuracy of the model.