24th Pacific Science Congress (PSC-24)

As global warming accelerates, extreme heatwaves have posed a growing societal concern for their substantial impacts on public health and ecosystem services. While previous studies have attributed these heatwaves to large-scale circulation anomalies, enhanced land-atmosphere feedbacks, and other processes, the relative contribution of each process remains inadequately quantified. Additionally, the general formation pathways of heatwaves across different regions are still insufficiently understood. Here we focus on two densely populated agricultural regions with large cities in northern and southern China: North China plain and Yangtze River basin, where two record-breaking summer heatwaves occurred in 2023 and 2022, respectively. With a Lagrangian temperature-anomaly decomposition and tracking framework, we quantify the contributions of various physical processes to multiple summer heatwaves in the two regions and reveal their distinct formation mechanisms. The results show that diabatic heating from land surface absolutely dominated the temperature anomalies in upper Yangtze River basin heatwaves, while the temperature anomalies originated from adiabatic subsidence increased significantly in North China heatwaves, which was comparable to the contribution of diabatic heating. The unprecedented intensities of 2023 North China and 2022 Yangtze River basin heatwaves were also dominated by different physical mechanisms. The former was rapidly triggered by accelerated subsidence under anomalous circulation patterns, while the latter was gradually exacerbated by enhanced land-atmosphere feedbacks due to widespread soil moisture deficits. Our findings provide a detailed, quantitative understanding of the physical mechanisms underlying the extreme heatwaves in different regions of China.
 

heatwaves,backward trajectory tracking,quantitative analysis,China