Fig. 1: Spatial distribution of drought intensity and drought duration identified by SPEI.

a Drought intensity and b drought duration. Mild drought (\(-1 < {{{\rm{SPEI}}}}\le -0.5\)), moderate drought (\(-1.5 < {{{\rm{SPEI}}}}\le -1\)), severe drought (\(-2 < {{{\rm{SPEI}}}}\le -1.5\)), and extreme drought (\({{{\rm{SPEI}}}}\le -2\)).