Identification And Application Of Thermal Dynamic Precursor Signals Of Torrential Rain In Warm Coastal Areas Of Guangdong

Warm-sector heavy rainfall(WSHR)features strong and concentrated precipitation with a sudden occurrence,which often happen in coastline.At present,the numerical weather forecast model in the world is very limited in the forecast ability of WSHR.Strengthening the understanding of the weather and climate characteristics of WSHR is conducive to improving the foundation of the rainstorm forecast in the warm region.Based on hourly rain gauge data at more than 30,000 automatic weather stations in China,in conjunction with the Climate Precipitation Center Morphing(CMORPH)precipitation product for the 2008–2017 and hourly ERA5 reanalysis data,the WSHR have carried from the rainy season in coastal area of south China by the objective screening.The environmental background of WSHR and its development mechanism is discussed from the thermodynamic perspective by dynamic composite analysis method.The results show that the maximum value of water vapor of the WSHR is concentrated below 800 hPa in the lower troposphere,and the maximum value center is located at 900 hPa.Before the occurrence of the WSHR,in the lower troposphere,the north of the South China Sea to the coast of Guangdong presents an obvious warm and moisture tongue,with sufficient unstable energy.With the cooperation of the boundary layer jet,the unstable energy and water vapor are transported to the mainland and convergence and uplift in the coast of Guangdong,forming a rainfall event.The scale analysis shows that the large-scale dynamic field and the small and medium scale thermal disturbance field play a leading role in the formation of the WSHR in the warm coastal area of Guangdong.In addition,through dynamic composite analysis method,this paper analyzes the prediction skills of the warm moisture tongue signal from the northern South China Sea to the coastal area of Guangdong for the WSHR dominated by warm advection,and presents the identification method of the forewarning signal of the rainstorm in the warm coastal area of Guangdong dominated by the warm wet tongue in the northern South China Sea,and verifies its prediction effect.The return results of the WSHR from 2008 and 2009 rainy seasons show that the warm and wet tongue in the northern part of the South China Sea was used as a precursor signal to forecast 17 cases.13 cases appear rainfall in the next four to six hours of rainstorm,4 case due to lack of water vapor conditions don't appear precipitation.The warm and wet tongue is the precursor signal of the WSHR in the warm coastal area of Guangdong.