Remote-Sensing Drought Monitoring in Sichuan Province from 2001 to 2020 Based on MODIS Data

In this study, four drought monitoring indices were selected to simulate drought monitoring in the study area and a correlation analysis was conducted using the self-calibrated Palmer Drought Index (sc-PDSI) to screen for the most suitable drought monitoring index for the study area. Then, the spatio-temporal variation characteristics of drought in the study area were discussed and analyzed. The results showed that the Crop Water Stress Index (CWSI) was most suitable for drought monitoring in the Sichuan Province. CWSI had the best monitoring in grasslands (r = 0.48), the worst monitoring in woodlands (r = 0.43) and the highest fitting degree of overall correlation (r = 0.47). The variation of drought time in the Sichuan Province showed an overall trend of wetting and the drought situation was greatly alleviated. In the past 20 years, the dry years in the Sichuan Province were from 2001 to 2007, in which the driest years were 2006 and 2007; 2012–2013 was the transition interval between drought and wet; any year from 2013 to 2020 was a wet year, showing a transition trend of “drought first and then wet”. The spatial distribution of drought was greater in the south than in the north and greater in the west than in the east. Panzhihua City and the southern part of the Liangshan Prefecture were the most arid areas, while the non-arid areas were the border zone between the western Sichuan Plateau and the Sichuan Basin. Looking at the spatial distribution of drought, “mild drought” accounted for the largest percentage of the total area (60%), mainly concentrated in the western Sichuan plateau. The second largest was “drought free” (33%), mostly concentrated in the transition area between the western Sichuan Plateau and the Sichuan Basin (western Aba Prefecture, Ya’an City, Leshan City and northern Liangshan Prefecture). The area of “moderate drought” accounted for a relatively small proportion (6%), mainly concentrated in Panzhihua City, the surrounding areas of Chengdu City and the southern area of the Liangshan Prefecture. The area of severe drought accounted for the least (1%), mostly distributed in Panzhihua City and a small part in the southern Liangshan Prefecture. The drought center ranged from 101.8° E to 103.6° E and 28.8° N to 29.8° N, with the movement trend of the drought center moving from the northeast to the southwest to the northeast