Accelerated Shifts from Heatwaves to Heavy Rainfall in a Changing Climate

Consecutive heatwave and heavy rainfall (HW-HR) events are occurring with increasing frequency in a warming climate. The time interval affects both environmental conditions and the regional recovery between two consecutive extreme events. However, the dynamics of the transition between consecutive HW-HR events remain poorly understood. In this study, we examine the changes in the time interval of consecutive HW-HR events in China from 1990 to 2019, using meteorological data from over 2,000 stations across mainland China. Our results reveal that the time interval has significantly shortened at 28.2% of the stations. The increased proportion of short-time events (STEs), defined by consecutive events with time intervals of 1 to 2 days, is the primary driver of this trend. From 1990 to 2019, the proportion of STEs increased significantly, at a rate of 2.2% per decade. We also find that climate change-induced anomalies in atmospheric variables during the consecutive HW-HR events may contribute to this rise in the proportion of STEs. Additionally, we assess changes in population exposure to STEs over the past two decades. Exposure has increased at more than three-quarters of the stations, with the increased STEs contributing to over 80% of the rise in exposure. Our findings highlight the need for policymakers to prioritize disaster response during consecutive HW-HR events and implement effective risk management strategies to mitigate population exposure to extreme events.