The heavy rainfall during the warm season over the Pearl River Delta region: Movements and early signals

Abstract

AbstractThe environments and movement, as well as the surface characteristics of heavy rainfall (HR), were examined based on 5‐year HR episodes collected from the surface observations during the warm season (April–September) from 2015 to 2019. The results showed that the HR generally exhibited eastward movement with average moving‐speed of 59 km⋅hr−1 over South China. The daytime HR exhibited more episodes and faster moving‐speed than the nocturnal HR. Both nocturnal HR and daytime HR were strongly influenced by the southerly wind during April–June over the Pearl River Delta (PRD) region. It showed a cyclonic wind pattern during the occurrence‐time of nocturnal HR and a strong early convergence belt at −3 hr of daytime HR between the southeasterly winds and the northeasterly winds over the north part of the PRD region, which might be related to the cold outflow from the upstream east‐moving convections. Another key characterization parameter of HR was the strong decrease of surface potential temperature over the PRD region, especially during July–September.