Different mechanisms for the extremely hot central-eastern China in July–August 2022 from a Eurasian large-scale circulation perspective

Abstract

In July and August of 2022, unprecedented and long-lasting heatwaves attacked central and eastern China (CEC); and the most affected area was in the Yangtze River (YR) basin. The extreme heatwaves and associated drought and wildfire had significant social impacts, but the underlying mechanisms remain unknown. Observational analysis indicates that the heatwaves were regulated by anomalous anticyclone in the mid-upper troposphere over northern CEC. Specifically, the easterly anomalies at the southern flank of the anticyclone caused air isentropic sliding and transported low moist enthalpy (cold and dry) air to the YR basin, contributing to anomalous sinking motions and extreme heatwaves. In comparison, heatwaves were more serious in August than in July due to stronger upper-level anomalous anticyclone and associated easterlies. Importantly, different mechanisms were responsible for the heatwaves in the two months. In July, the relatively weaker anticyclonic anomaly over northern CEC was dominated by the forcing of diabatic heating over northwestern South Asia (NWSA), corresponding with the record-breaking rainfall in and around Pakistan. In August, a powerful anticyclonic condition for the CEC heatwaves originated from an extreme silk road pattern (SRP), superposing the effect of NWSA diabatic heating due to persistent downpour. We notice that another upstream anticyclonic node in the SRP also created heatwaves in Europe. Therefore, the CEC extreme heat was actually associated with other concurrent extremes over the Eurasian continent through large-scale atmospheric teleconnections in 2022.