Asymmetric Spring–Summer Responses of Interannual Dry–Wet Transitions in Eastern Asia and North America Under Global Warming

Abstract Under global warming, accelerated hydrological cycle and enhanced climate variability are expected to increase the risk of interannual dry–wet transitions (IDWTs). This study employs the Standardized Precipitation Evapotranspiration Index (SPEI) to examine historical characteristics and future changes of IDWTs over eastern Asia and North America during boreal spring and summer. Over the past six decades, springtime IDWTs are concentrated in eastern China and the southeastern United States, whereas summer transitions intensify and expand northward across eastern Asia but decrease and shift poleward over North America. Springtime IDWT frequency increases by over 50% in most regions of eastern Asia and eastern North America, whereas summer exhibits strong spatial heterogeneity, with continued but weaker increases over eastern Asia and decreases over the mid‐latitudes of North America. Further analyses demonstrate that future changes in IDWT frequency are jointly influenced by dry–wet tendencies and the historical climatological dry–wet background.