samad khosravi yeganeh; mostafa karampour; Behrouz Nasiri
Abstract
In the coming years, drought is one of the potential threats to low rainfall countries, especially Iran. Iran has always faced big and small droughts. The geographical location and natural conditions of the country are such that severe and weak droughts have occurred in it. Evaluating the effects of ...
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In the coming years, drought is one of the potential threats to low rainfall countries, especially Iran. Iran has always faced big and small droughts. The geographical location and natural conditions of the country are such that severe and weak droughts have occurred in it. Evaluating the effects of drought on vegetation is very important. In order to reduce damages and consequences caused by drought, drought monitoring using remote sensing method is considered in most countries because of its advantages. In this study, in order to reveal the effects of precipitation on vegetation in Iran, the precipitation data of 143 synoptic meteorological stations of the country were used to calculate the monthly average of the Standard Precipitation Index (SPI) in the period 2000-2021. Then, using visible infrared images (VIIRS) as a weekly average in the period of 2013-2021 (April 1st to the end of July every year) obtained from the Suomi NPP sensor, the drought condition of the vegetation was investigated. Based on the obtained results, it can be said that the vegetation cover in 2015 and 2021 was more affected by drought than the other investigated years. The most severe vegetation drought occurred in 2021. In 2016, 2019 and 2020, vegetation was in more favorable conditions. The correlation of SPI with NDVI, VCI, TCI and VHI was calculated as 0.1906, 0.038, 0.016 and 0.002 respectively.
mostafa karampour; samad khosravi yegane; hamed heidri
Abstract
IntroductionIn each region, drought conditions vary from moderate to severe and with different durations, which require continuous and operational monitoring. The longer a drought occurs, the greater its effects on vegetation and water resources, and the more severe the drought, which can limit human ...
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IntroductionIn each region, drought conditions vary from moderate to severe and with different durations, which require continuous and operational monitoring. The longer a drought occurs, the greater its effects on vegetation and water resources, and the more severe the drought, which can limit human services and alter natural systems. The effects of drought include habitat destruction for wildlife and water quality, reduced access to water resources, etc. and as a result, disruptions such as fire incidents and other natural disasters increase. ). Vegetation in each region, especially in different regions of Lorestan province, is at risk of numerous fires every year due to the lack of rain and dryness of the environment. For this reason, the issue of revealing and identifying fire-prone areas in relation to the most important climatic element (rainfall) has been selected and carried out, which can facilitate appropriate and preventive measures to protect vegetation areas. In this research, a combined method has been used.Material and methods:In this study, an attempt has been made to investigate the drought condition of vegetation in Lorestan province by using Suomi NPP infrared images using NDVI, VCI and TCI indices. The studied period of 2013-2021 corresponds to the first of April to the end of July (week of 13-26 AD) as a weekly average. The monthly average of Standard Precipitation Index (SPI) using precipitation data, the use of monthly precipitation data from Aligoderz, Durood, Khorramabad, Borujerd, Noorabad, Kohdasht and Azna weather stations was done to analyze the precipitation situation well and separate dry and wet months from each other. become Then the correlation coefficient of SPI index with each vegetation index (NDVI, VCI and TCI) is calculated.Results and discussion:Based on the rainfall data recorded in the meteorological stations of Lorestan province, it can be said that there is no rainfall in the study area in the summer season (July, August and September) and only in the autumn, winter and spring seasons. Therefore, the water year in Lorestan province starts approximately from the third decade of September and continues until the second and third decade of June every year. This indicates the very dry air and lack of humidity. Dry air or lack of humidity and increase in temperature provide the necessary conditions for causing fire in the province. In this article, they put a dry season in the summer season of Lorestan province and August is the driest month of the year.ConclusionThe results of this research showed that the vegetation in Lorestan province is always facing the risk of fire and this is very high in the years when there is a lack of rainfall, in different months. It was proved that if there is a lack of rainfall in the first months of the water year, there is a risk of vegetation fire even in the cold months of the year, and this risk increases significantly in the hot months of the year, which is the case in 2021. there have been. SPI calculations showed that the months of July, August and September are negative in Lorestan province. The results show that the best indicator is based on satellite images for monitoring vegetation drought and fire risk in the study area (TCI). In the years 2013 and 2015, the highest fire risk occurred in the western and central regions of Lorestan province. In 2021, the most severe fire risk has occurred in vegetation in the studied area. Due to the large changes and dispersion of vegetation indicators effective in the occurrence of fires in terms of time and place, Spearman's non-parametric correlation has been used.Keywords: Vegetation fire, drought , precipitation, infrared images, Lorestan province
morteza Sharif; aboozar kiani
Abstract
Forest fires worldwide cause severe damage to vegetation, soil and natural habitats, resulting in direct and indirect negative environmental impacts such as deforestation, climate change and drought. Therefore, identifying and determining the hazards of vegetation that suffer from fire is crucial for ...
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Forest fires worldwide cause severe damage to vegetation, soil and natural habitats, resulting in direct and indirect negative environmental impacts such as deforestation, climate change and drought. Therefore, identifying and determining the hazards of vegetation that suffer from fire is crucial for their management and development. The proliferation of remote sensing images such as the active fire products of the Terra and Aqua satellites over the past two decades has been one of the most essential methods in detecting these fires. However, the active fire product of the MODIS sensor in previous studies has shown that they alone do not provide good results in fire-affected areas. Therefore, it is necessary to evaluate vegetation with basic maps. The aim of this study was to investigate two types of plant products and to discover the active fire of MODIS sensor and FNF-JAXA forest and non-forest cover maps for better separation of burnt areas of vegetation in Iran between July 1 and 160 2020. The results show the highest area of fire on Julius 144 with more than 49 thousand hectares and Julius 128 with more than 45 thousand hectares. However, the largest area of the fire, forest cover is estimated at 120 to 160 in 2020 with more than 14 thousand hectares. Khuzestan province had the highest area of fires in the period under study that most of these areas in agricultural lands and the three provinces of Fars, Kohgiluyeh and Boyer-Ahmad and Bushehr had the highest area of fires in forest cover. The highest frequency of fires was observed in agricultural lands, the main reason for which could be human intervention. The evaluation of the results showed that the use of the FNF-JAXA product (accuracy of 87.4% and a Kappa coefficient of 0.85) compared to MODIS products (accuracy of 80.3% and a Kappa coefficient of 0.78) in the separation of forest areas has better capabilities. However, the ability of MODIS products to distinguish between pasture and agricultural vegetation is an important advantage, which the FNF-JAXA product does not have. In general, the findings of the research show that the MODIS product and FNF-JAXA maps can be used as reference maps to distinguish different types of vegetation that are subject to fire, in damage assessment and management.
Kamal Omidvar; massumeh nabavi zadeh; Ahmad Mazidi; HamidReza Ghaffarian Malmiri; Peyman Mahmoudi
Abstract
Drought monitoring is critical for early warning of drought hazard. This study is attempted to develop remote sensing drought monitoring index (VDI), based on Accuracy of different bands of Moderate Resolution Imaging Spectroradiometer data MODIS, VDI focuses about the vegetation water stress. Spectral ...
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Drought monitoring is critical for early warning of drought hazard. This study is attempted to develop remote sensing drought monitoring index (VDI), based on Accuracy of different bands of Moderate Resolution Imaging Spectroradiometer data MODIS, VDI focuses about the vegetation water stress. Spectral studies have demonstrated that due to the large absorption by leaf water, shortwave infrared reflectance (SWIR) is negatively related to leaf water content. Being sensitive to leaf water content, SWIR is widly utilized to construct various remote-sensing indices for example VDI for reflecting vegetation water content, . In this study, Vegetation Drought Index (VDI) was evaluated Based on the sensitivity rate to moisture by shortwave infrared reflectance bands SWIR 5 and 6 (VDI5 and VDI6). The data included the MODIS sensor images from Terra satellite in a period of nineteen years from 2000 to 2018 and Precipitation data are obtained from the Global Land Data Assimilation System (GLDAS), in Sistan & Balouchestan Province, Pearson correlation coefficient was used to evaluate the accuracy of the Drought spatial distribution maps calculated based on the two bands.Results indicate high significant correlation rate between VDI6 and Precipitation data . Study also showed that shortwave infrared band 6 (SWIR) is more sensitive to agricultural drought than band 5,in Sistan and Baluchestan province . The study recommends to use VDI index with and 6 for better early detection and monitoring of agricultural drought in operational drought management programmes.
Mehran Shaygan; Marzieh Mokarram
Abstract
Due to the fact that droughts can affect both water quality and quantity, the purpose of this study is to determine the effect of droughts on water quality and quantity in Northern Fars province, Iran, based on drought indicators. The drought indices PCI, TVDI, and NDVI are used to study drought from ...
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Due to the fact that droughts can affect both water quality and quantity, the purpose of this study is to determine the effect of droughts on water quality and quantity in Northern Fars province, Iran, based on drought indicators. The drought indices PCI, TVDI, and NDVI are used to study drought from 2000 to 2020. Also, the kriging method is used to generate zoning maps of elements in water (Ca, Cl, EC, K, Na, Mg). Then, using the neural network (MLP) method, the amount of elements in the water is predicted based on drought indices. Based on the values of the drought indicators, the trend of drought changes in the region is increasing from 2000 to 2020, with the southern areas of the region experiencing a more acute drought than the rest of the region. In addition, the zoning map of the elements in water indicated that salt concentrations are higher in the southern parts than in the northern parts. Correlation between drought indices and the amounts of elements in water showed that Ca has a high correlation (R2= 0.820) with TVDI index, and also Cl, EC, K, Na, and Mg have significant correlations (R > 0.8) with the index. Using drought indicators, MLP results for predicting water quality status show that southern regions have more solutes and lower water quality. Furthermore, the R2 values of the model for predicting the elements Cl, EC, K, Na, Mg, TDS, TH using PCI index equal to 0.85 and for Ca using TVDI index equal to 0.71, which indicates high accuracy.
vahid ahmadi; Abbas Alimohamadi
Abstract
Drought evaluation is important in terms of spatial and temporal for planning to reduce damages in the Kordestan province. In this research, Standardized Precipitation Index and the Enhanced Vegetation Index have been used from the extracted satellite images for determinants of drought. so, the statistical ...
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Drought evaluation is important in terms of spatial and temporal for planning to reduce damages in the Kordestan province. In this research, Standardized Precipitation Index and the Enhanced Vegetation Index have been used from the extracted satellite images for determinants of drought. so, the statistical data of Meteorological stations including maximum monthly temperatures, total annual precipitation and the images of MODIS sensor have been employed. By comparing meteorological parameters such as average annual temperature, rainfall and the comparison of maps of the Standard Precipitation Index and Enhance Vegetation Index, the condition of drought has been investigated in the region in a 17-year period. The results of the two SPI and EVI indices indicate that the drought is due to rain changes have in the west-to-east direction. This phenomenon is more severe in the eastern regions whereas vegetation sensitivity and the fluctuation of its variations have been affected by precipitation changes in the north-to-south direction over the region. In this way, the southern regions have shown higher sensitivity. Southern regions are generally more vulnerable to droughts, especially in the south-east of the province. Regions with high drought sensitivity make up about 10 percent of the area regarding the regions in the province, whereas 91 percent of the area of regions with very high drought sensitivity is places where the landuse involves growing wheat with rain water.
Maedeh Behifar; a.a Kakroodi; Majid Kiavarz; Farshad Amiraslani
Abstract
Drought is one of the most important natural disasters in the country, with devastating environmental and economic effects. Most drought studies have focused on drought severity and other drought characteristics have not been usually investigated. In this research, for the first time, the capability ...
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Drought is one of the most important natural disasters in the country, with devastating environmental and economic effects. Most drought studies have focused on drought severity and other drought characteristics have not been usually investigated. In this research, for the first time, the capability of meteorological drought indices and satellite data are combined and applied to study drought in inland and coastal basins. For this purpose, the SPI index was calculated by using TRMM satellite precipitation products and then, the drought characteristics such as severity, duration, magnitude, and extent were spatially studied. The results showed that the correlation coefficient between the SPI calculated from the image and the station data was 0.94. The maximum intensity of drought in the study area was -4.19 which occurred in December 2010. Furthermore, the frequency of extreme droughts in 6- and 12-months timescales was higher in the inland area compared with the coastal area. Moreover, in the six-month timescales, 60 percent of drought events had a magnitude of -18.3 or less. The results showed that it is possible to obtain the extent of drought by using satellite imagery which cannot be calculated by other methods. Besides, by using satellite images, drought characteristics could be studied spatially at the basin scale, which is not possible by traditional methods. The results showed the advantage of using satellite precipitation images in the drought study
Mahshid karimi; Kaka Shahedi; Tayebe Raziei; Mirhassan Miryaghoobzadeh
Abstract
Drought is one of the natural disasters that may occur in any climate. In recent decades, Iran has been affected by severe droughts and its harmful effects in various sectors, such as agriculture, environment and water resources of the country. Today, vegetation indices, which are obtained through remote ...
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Drought is one of the natural disasters that may occur in any climate. In recent decades, Iran has been affected by severe droughts and its harmful effects in various sectors, such as agriculture, environment and water resources of the country. Today, vegetation indices, which are obtained through remote sensing technology, are used to identify and analyze agricultural droughts. Accordingly, the aim of this study was to investigate the effectiveness of NDVI, EVI and VCI vegetation indices in agricultural drought identification and analysis in Karkheh basin. In order to calculate these indices, MODIS sensor Images (Terra satellite, MOD13A2 product) were used during the 2000-2017 statistical period. The accuracy of these profiles was evaluated with the ZSI index calculated at 11 meteorological stations located in Karkheh basin for the statistical period of 2000-2017. The results showed that the changes of NDVI, EVI and VCI in the studied stations were approximately the same during the statistical period. Based on NDVI, EVI and VCI values, the lowest and highest vegetation cover was observed in 2000, dehno station and 2001, helilan-seymareh station, respectively. The ZSI survey showed that most stations Faced with droughts from 2000 to 2008, and the most severe drought occurred in 2008, nazarabad station. Then, in order to validation of the results, the vegetation indices with ZSI index were evaluated. Pearson correlation between mean vegetation indices of NDVI, EVI and VCI with mean ZSI was 0.766, 0.725 and 0.776, respectively, and all vegetation indices with ZSI index are significant at 0.99% confidence level. As seen, according to the results, the ZSI index confirms the results of NDVI, EVI, and VCI. So, according to the results, there is no conformity of meteorological and agricultural droughts in all years, Therefore, in addition to other precipitation, climate variables should also be considered.
hossein Nikpey; Mehdi Momeni
Abstract
Drought is an important phenomenon which can be monitored based on weather data obtained from weather stations and remote sensing data. Remote sensing methods have offered significant relative advantages compared to the other methods for monitoring drought . Also , several drought indicators have provided ...
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Drought is an important phenomenon which can be monitored based on weather data obtained from weather stations and remote sensing data. Remote sensing methods have offered significant relative advantages compared to the other methods for monitoring drought . Also , several drought indicators have provided in remote sensing for monitoring drought , but none of the common indicators in remote sensing did not have generalizability of time , climate and altitude and it is necessary the performance quality of these indexes 1) in climates, 2) in altitudinal zoning examined .This study also proved this hypothesis , to identify appropriate indicators in every altitudinal zone , and in every region the index considered the appropriate season to evaluate indexes . In this study , drought indices ,VCI ,VDI ,TCI and TVDI by LST parameter , NDVI and EVI have been evaluated. To evaluate climate and altitudinal indicators , first in the whole country and then in Hamadan province , climate and altitudinal zoning done and drought indexes for different climates and altitude was determined in two forms pixel-based and object-based (polygons) and compared to precipitation data TRMM sensors . The operation of drought indexes were analyzed to drought evaluation by taking account climate type , data acquisition season , altitude and area . The results of this research shows lack of generalizability of all indictors in terms of climate , altitude and time indicators and for example , in pixel evaluating of hot and dry climate , the highest correlation between VCI index and precipitation data was in June and the lowest correlation is in December.
