Investigation of indicators resulting from remote sensing technology in drought assessment using MODIS images (Case study: Qom, Isfahan, Chaharmahal and Bakhtiari and Markazi provinces)

In this study, the relationship between meteorological drought index (SPI index) and remote sensing indices of VCI, TCI and VHI in Isfahan, Chaharmahal and Bakhtiari, Markazi and Qom provinces has been investigated. In this regard, using the satellite images of Modis Terra sensor and precipitation data of rain gauge and synoptic stations located in the study area, the detection of changes occurred over a period of 10 years was calculated. For this purpose, four months (April, May, June and July) were selected as a sample by reviewing the data of existing stations and using the standardized precipitation index (SPI) model. In this study, due to time accuracy, high spectrum coverage, ease of access, no need for atmospheric correction and ground reference, images with code (MOD11A2 and MOD13A2) of Modis satellite sensor products related to the years 2011 to 2020 due to Confidence of wet and drought phenomena was used and then SPI index was compared with VCI, TCI and VHI indices in combination. The results of drought monitoring showed that during this ten-year period, there was severe drought in some years, and in the same year, less rainfall occurred. In 2020, for example, the drought was very severe, and in 2011 it was very wet. The results of the correlation between SPI index and remote sensing indices showed that SPI index has the highest correlation with VCI index at the level of 0.01. It was found that MODIS images and constructed indices have the necessary capability for drought monitoring. The results of this study can be a good option for decision makers to monitor, investigate and resolve drought conditions and double the need to define an index.