Analyses and applications of the precursor signals of a kind of warm sector heavy rainfall over the coast of Guangdong, China

Abstract

Based on the observational hourly precipitation data with high-resolution and ERA5 reanalysis, the thermodynamic characteristics of warm sector heavy rainfall (WSHR) events over coastal areas of Guangdong are studied by composite analysis. The results show that the WSHR water vapour is mainly concentrated below 800 hPa in the lower troposphere with the maximum center located at 900 hPa, which is favorable for the warm and moist energy accumulation. The boundary layer jet (BLJ) and synoptic-system low-level jet (SLLJ) prevail over northern part of the South China Sea before precipitation happens, and the exit of BLJ locates at the entrance of SLLJ. The suction effect, together with the coastline convergence, tends to increase local upward motion and trigger local convection over coastal areas of Guangdong. The warm and wet tongue indicated by θse over northern part of South China Sea, which represents the warm and moist energy at low levels, has close relationship with WSHR events. According to analyzed thermodynamics of WSHR, the objective identifications of precursor signals for WSHR over coastal area of Guangdong are proposed from perspectives of low-level jet, warm and moist tongue and dynamic convergence in the lower troposphere, which are further demonstrated effective via hindcasts for 2008 and 2009 and can be pragmatically employed as a scientific reference for the local WSHR forecasting.