Evaluation and Monitoring of Drought in Qazvin Plain Using MODIS Based Indicators in Google Earth Engine

Drought is a natural phenomenon that affects different climatic, hydrological and environmental systems. Drought modeling is an important issue because it is considered important and necessary in order to contain or reduce its effects and to preserve water resources and social management. In this research, by using multiple indicators based on MODIS and CHIRPS precipitation data set, to investigate the spatial and temporal characteristics, intensity and frequency of drought in Qazvin plain in a 20-year period in order to identify and describe drought based on different indicators. The results of the surveys based on the TCI index showed that in 2004 and 2020, about 63% and 76% of the plain is under the influence of moderate to severe drought, with the difference that the result of the VCI index survey in the same year The analyzed data show that only 54.1% and 67.3% of the affected area show similar drought intensity levels. Therefore, the TCI index has estimated relatively more drought stress than the VCI index. From 2014 onwards, the eastern and southeastern areas of the plain are gradually facing an increasing trend of drought, and in the years 2018 to 2020, drought has been faced with much greater intensity. In examining the correlation between different indices, the PDSI index has the highest correlation with the SPI-1 index with a numerical value of 0.74. Qazvin plain is currently exposed to drought due to climate changes and lack of proper productivity in the use and distribution of water resources. Therefore, it is recommended that continuous monitoring of drought and the use of early warning systems are effective in preventing the possible occurrence of severe drought events in the future and the possibility of implicit risks for Qazvin Plain.