Drought monitoring using MODIS data and its comparison with SPI meteorological index in short periods (Case study: Jaz_Murian basin)

Drought is one of the most important threats for agricultural production in the world, espatially in Iran. This phenomenon has started with reduction of precipitations that lead to a decrease in soil moisture and an increase in soil surface temperature, which affect the vegetation growth. The purpose of this study was to investigate droughts in the Jaz_Murian basin by VHI, VCI, TCI and SPI indices using MODIS satellite imagery and meteorological data. For this purpose, the LST products (MOD11A1) and vegetation products (MOD13A1) were selected from 2000 to 2018 at the same time (the first week of March). The VHI and VCI maps were produced and the drought occurrences with critical and very severe classes were identified. Also, the SPI index was calculated using precipitation data in Kahnooj synoptic meteorological station. According to the VHI index, the results showed that over 75% of the study area was classified as the severe, very severe and extreme classes of drought and has suffered from drought in 2001, 2002, 2006, 2009, 2012, 2016 and 2018. Very severe and extreme classes are covered the center of the region, and the eastern and southeastern parts of the basin that likely is related to the rainfall reduction and topographic characteristics of the area and poor vegetation. In comparison with the SPI meteorological index in the short periods (one month, three months, six months), the VHI index indicates the more correlation with the six-month SPI. According to the results obtained in this study, a large part of the study area is located in severe and very severe of drought classes which need more attention to water resource management in this region.