Upwind Droughts Enhance Half of the Heatwaves Over North China

Abstract

Antecedent or concurrent drought conditions are recognized as important factors for triggering or intensifying heatwaves through local land-atmosphere interaction, but recent studies show nonlocal effects for a few mega-heatwaves. To quantify the impacts of upwind droughts on all related heatwaves, a Lagrangian heat tracing model driven by reanalysis data is employed over North China, a region influenced by monsoon and westerly significantly. Through analyzing 17 major heatwaves over North China during 1979–2019, we find eight of them are significantly enhanced by upwind droughts. The advected sensible heat that results from circulation anomalies and upwind soil moisture droughts contributes to 71% of the heat for heatwaves. For eight drought-related heatwave events, the upwind soil droughts from southern and western source regions contribute to 67.9% of the heat anomalies, with 3/5 of them coming from the south. This study suggests that upwind droughts are important for early warning and adaptation for heatwaves.