Extraordinary hot extreme in summer 2022 over the Yangtze River basin modulated by the La Niña condition under global warming

Abstract

A widespread and prolonged hot extreme hit the Yangtze River basin in summer 2022, with 300 sites established new temperature records and nearly 96% stations endured more than 40 hot days. From the perspective of the combination effect of the global warming and La Niña condition, potential mechanisms of the hot extreme were investigated. Such a record-breaking hot extreme was caused by an extremely strong and westward-shifted western Pacific subtropical high (WPSH). The global warming effect contributed primarily to the abnormal hot days in the Yangtze River basin, coupled with the modulation of the La Niña condition. The sea surface temperature anomaly pattern under La Niña condition favored more convection activities over the western Pacific, encouraging an enhanced and westward-extended WPSH. In addition, an observation-based attribution analysis indicates that anthropogenic warming may increase the probability of such extensively persistent hot extreme by 1.8 times.