Fig. 1: Monthly SPEI, percentage of area in drought and maps of SPEI trends and the 2022 drought.
a,b, The quasi-global (50° S to 50° N) average HRSPEI (a) and global percentage of area in droughts (b). c, The trend in 6-month HRSPEI for 1981–2022 (z-units yr−1), with non-significant trends (P > 0.05) marked in grey for visualization. d, The 6-month HRSPEI values for the record-breaking drought in August 2022 (z-units). The time series uses HRSPEI (0.05°), CRU-TS (0.5°) and ERA5 (0.25°), with HRSPEI being the ensemble mean of MSWEP_hPET, MSWEP_GLEAM, CHIRPS_hPET and CHIRPS_GLEAM (1981–2022). CRU-TS covers 1901–2022 and ERA5 spans 1950–2022. The time series are averaged over tropical and subtropical land areas (50° S to 50° N), excluding regions with average annual rainfall below 180 mm. For regions above 50° N, the spatial trend is based on the mean of MSWEP_hPET and MSWEP_GLEAM, as CHIRPS is available up to 50° N. The vertical lines indicate the period from 1950 to 1980, showing higher positive SPEI values based on ERA5 and CRU-TS compared with 1981–2022.
