Attribution analysis of the persistent and extreme drought in southwest China during 2022–2023

Abstract

Southwest China, particularly Yunnan Province and neighboring regions, experienced a severe and persistent drought from Oct 2022 to May 2023. Precipitation and surface soil moisture during this drought were both the lowest recorded for the same period since 1950. The Standardized Precipitation Evapotranspiration Index (SPEI) also reached its lowest level since 1950 at −2.76. Quantitative analysis shows that precipitation deficit, precipitation-induced potential evaporation (PET) increase, and residual PET contributed 71.36%, 7.05%, and 21.59% to the drought, respectively. Using data from the CMIP6 Detection and Attribution Model Intercomparison Project (DAMIP), we found that anthropogenic forcing increased the likelihood of a PET anomaly such as the one during the drought by about 133 times, with a fraction of attributable risk (FAR) of 0.99 [0.98, 1.00]. For the precipitation anomaly, we obtained a FAR of 0.26 [−1.12, 0.70], suggesting that anthropogenic forcings may have little impact. The extreme drought also increased the risk of fires, with the Fire Weather Index reaching its second-highest value since 1950 and abnormally high burned areas observed by satellites.