Wintertime extreme precipitation event over southern China and its typical circulation features

Abstract

This study objectively defined an extreme precipitation event (EPE) over southern China and investigated the associated typical circulation pattern on the intraseasonal time scale. The occurrence of the EPE resulted from the joint operations of anomalous circulations over the subtropics and mid-high latitudes. During the EPE, simultaneous enhancements of the trough over the Bay of Bengal (BBT) and the Western Pacific subtropical high (WPSH) facilitated the abundant water vapor conditions over southern China, whereas the weakened East Asian major trough (EAT) led to a moderate cold air invasion to that region, producing a persistent convergence zone over southern China. Wave train pattern in North Atlantic and Europe may be viewed as precursory signals for the EPE over southern China, and it contributed to the Rossby wave propagation in association with the EPE. These wave packets propagated toward East Asia mainly along the North African-Asian subtropical westerly jet waveguide. Low-frequency disturbances along this waveguide contributed to the enhancement of the BBT and WPSH and the weakening of the EAT, constituting favorable circulation conditions for the EPE.