Monitoring agricultural drought in Iran using time series of vegetation health index

In this study, in order to examine the severity of drought risk in Iran during ۱۸-year period (۲۰۰۱-۲۰۱۸), we used rain meteorological data of ۱۷۶ synoptic meteorological stations, ground surface temperature product (MOD۱۱C۳) and vegetation product (MOD۱۳C۲) of Moderate Resolution Imaging Spectro radiometer (MODIS). The study results show that the highest drought severity occurred in ۲۰۰۱ and ۲۰۰۳, in ۲۰۰۱ in spring ۸۵.۸% and in the summer of ۲۰۰۳, ۹۳.۸% of the country was affected by different degrees of drought. During the ۱۸-year period, the highest percentage of drought was related to mean (۴۵.۳%), mild (۲۵%), and severe (۸.۹%) classes, and no drought (۲۰.۷۹%), respectively. The results indicate that in the whole country, there is no severe drought region in the studied period. According to the map of the rainy regions, Iran's rainfall is highly dependent on the roughness, latitude and frequency of the arrival of synoptic systems in the region. The spatial rainfall map in Iran is well suited to VHI drought maps. The regions that receive less than ۱۰۰ mm of rainfall represent the real deserts of the country. In these regions, severe drought conditions occur. The rainy regions between ۱۰۰ and ۲۰۰ mm, in terms of drought conditions, are in the mean class of drought. The rainy regions with a range of ۲۰۰ to ۳۰۰ mm are in the mild class of drought and rainy regions with more than ۳۰۰ mm are usually not affected by drought stress.

کلیدواژه ها:

Drought ، Vegetation condition index ، Temperature condition index ، Plant health index ، Iran