The joint influences of the South Asian jet wave train and Eurasian teleconnection on the wet-cold extreme over South China in February 2022

Abstract In February 2022, an extreme wet and cold event hits South China, with the regional precipitation ranking the second highest record, while the temperature ranking the third lowest since 1979. In this study, the physical mechanisms of this extreme event are investigated from the perspective of multiple timescales interaction. Results show that the strong confrontation between the warm and moist air advection by the India-Burma trough (IBT) and the invasion of cold air activity related to strengthening of the East Asian winter monsoon (EAWM) is the key to trigger this extreme event. Further analyses show that the multi-timescale coupling of the South Asian jet wave train and Eurasian (EU) teleconnection is the main reason for the strong cold and warm-moist air flow. The EU teleconnection on both intraseasonal and synoptic timescales plays a key role in triggering this extreme event by strengthening the EAWM. On synoptic timescale, not only EU teleconnection, but also the South Asian jet wave train plays a key role. They show a stronger intensity on this timescale and their coupling are obvious. The South Asian jet wave train enhances the moisture supply by deepening the IBT, which further conflicts with the strong EAWM modulated by EU teleconnection over South China, leading to this extreme wet-cold event. The forecast skills in the Subseasonal to Seasonal (S2S) prediction project models of this event are evaluated in this paper, results show that the ECMWF model can successfully predict the extreme precipitation by capturing the coupling of the two wave trains with a 5 days lead time.