Upwind droughts enhance heat waves in Eastern China

Heat wave is one of the most severe natural disasters in the mid-latitude regions. Due to climate change and urbanization, heat waves have been intensified in the past, and are projected to be more severe in the future. Droughts and heat waves usually occur simultaneously, which are referred to as compound extreme events. Antecedent or simultaneous droughts enhance heat waves through local land-atmosphere interaction, but a few case studies show that upwind droughts can have a significant impact on heat waves through sensible heat advection. In order to systematically study the impact of upwind droughts on heat waves, this study uses a Lagrangian integrated trajectory model driven by reanalysis data to analyze the heat wave events in northern part of Eastern China from 1979 to 2019. We find that half of the heat waves are enhanced by upwind droughts. For the related heat waves, the upwind droughts contributed to 67.9% of the heat anomalies. The impact of flash drought on heat waves in Eastern China is also being explored, with particular interest to extract heat wave signals from antecedent flash drought to provide early warning for extreme heat waves over downwind areas.