Future drought projection of Southwestern China based on CMIP5 model and MCI index

In the past 50 years, Southwestern China has suffered from frequent, intense droughts. MCI (meteorological drought composite index) was calculated, and ArcGIS Spatial Analyst was run in the present study. The simulation performance was compared between different CMIP5 models. Then we projected the temporal and spatial distributions of drought in the intermediate path (RCP4.5 scenario) in the two time periods (2018-2058 and 2059-2099) between 2018 and 2099. The results showed that (1) the number of days with moderate drought and above increased in Southwestern China in both two time periods. The high-value regions were mainly found at the borders between Sichuan and Yunnan Province from 2018 to 2099. The annual number of drought days was generally above 150d. The low-value regions were mainly found in some parts of southeastern Sichuan, Chongqing, and the large parts of Guizhou. The annual average number of drought days was generally below 100d; (2) At phase P1 (from 2018 to 2058), the projected spatial distribution of drought severity was generally consistent with that of the annual average number of days with moderate drought and above. At phase P2 (from 2059 to 2099), the high-value regions of drought severity were still primarily found at the borders between Sichuan and Yunnan Province. The low-value regions were mainly found in the large parts of Chongqing and Guizhou. As time progressed, the high-value regions of drought severity expanded, and the drought was aggravated; (3) At phase P1, the high-value regions of drought frequency were mainly found at the borders between Sichuan and Yunnan. In these regions, the drought frequency was above 80%. The low-value regions of drought frequency were mainly found in parts of western Guizhou and central and eastern Sichuan. In these regions, the drought frequency was below 20%. At phase P2, the high-value regions of drought frequency were generally found in Yunnan Province and southwestern Sichuan. In these regions, the drought frequency was above 60%. The low-value regions of drought frequency were mainly found in Chongqing and northern Guizhou. In these regions, the drought frequency was below 20%. From phase P1 to P2, the high-value regions of drought frequency expanded, and the drought frequency increased. The low-value regions of drought frequency shrank in size. The drought frequency also decreased. Taken together, the drought in Southwestern China was aggravated and occurred more frequently according to the projections from 2018 to 2099. Our research findings offered important guidance for drought early warning and prevention in Southwestern China.