The Heavy Rainfall During The Warm Season Over The Pearl River Delta Region: Movements And Early Signals

The 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.