Changes in Teleconnection Patterns and Land–Atmosphere Coupling Amplify the Spring–Early Summer Heatwaves Over Southwestern China

Abstract

The frequency and intensity of heatwaves over southwestern China during spring and early summer have been increased significantly during 1980–2022. Until now, the physical mechanisms for these changes in heatwaves remain unclear. Here, we show that these increases in heatwaves can be attributed to the changes in both local soil moisture–temperature coupling processes and teleconnection patterns across Eurasia. On the one hand, the third dominant mode of teleconnection patterns across Eurasia exhibits more pronounced and meridionally-elongated features after the 2000s, leading to more southeastward-shifted positive geopotential height anomalies towards southwestern China, favouring increases in the regional heatwaves. On the other hand, the intensified coupling strength of soil moisture–temperature further amplifies the heatwaves over southwestern China, in particular for compound drought and heatwave (CDHW) events. This intensified soil moisture–temperature coupling is attributed to the identical phase transitions of heat anomalies and temperature anomalies after the 2000s. Distinct characteristics and drivers of CDHW and non_CDHW over southwestern China are also discussed.