Escalated Risk of Concurrent Eurasian Heatwaves Under Recurrent Rossby Wave Patterns

Abstract

Concurrent heatwaves, featured by simultaneous occurrences of extreme heat in separate regions, pose significant risks to natural ecosystems and human society. In August 2022, unprecedented heatwaves struck central China and west Russia concurrently, resulting in severe energy crisis, numerous financial losses, and fatalities. Through synoptic-scale analysis, we identify a pivotal role of recurrent Rossby wave packets (RRWPs) in shaping the event by repeatedly forming ridges and troughs over the same key areas. In this study, we further extend the investigation of the influence of RRWPs on heatwave occurrences in these two targeted regions over the past 44 years. Using a self-organizing map to identify the RRWP patterns, we find that RRWPs with ridges over central China are closely associated with a marked increase in heatwave probabilities in both central China and western Russia. Specifically, the regional-mean likelihood of heatwaves increases by factors of 3.0 and 2.6, respectively, relative to the climatology. Notably, the effect of RRWPs on the occurrence of concurrent heatwaves across both regions is more pronounced than on regional events alone. For example, during RRWPs, the likelihood of concurrent heatwaves affecting at least 20% of both target regions exceeds 10 times the climatological average. Our findings underscore the significant role of RRWPs in triggering concurrent Eurasian heatwaves and suggest promising synoptic predictability for such extreme events.