Characteristics of Rainfall Distribution and Moisture Transport during the Pre-flood Season in Heyuan City in 2024

LI Siping; LIAO Yongpei; LIU Yanbo; TANG Ninglin; DUAN Haihua; SHAN Xueke

doi:10.3969/j.issn.1007-6190.2025.06.004

Abstract：To understand the precipitation distribution and moisture transport characteristics during the pre-flood season in Heyuan City,this study investigates the precipitation distribution and moisture transport characteristics during the pre-flood season(April-June)in Heyuan City.Using ERA5 reanalysis data,rain-fall observations from 232 meteorological stations in Heyuan,and the HYSPLIT model driven by GDAS data,we analyze the water vapor transport over South China and the rainfall distribution in Heyuan during the 2024 pre-flood season.Monthly water vapor transport trajectories were simulated for the study area.The results in-dicate that precipitation in Heyuan during the 2024 pre-flood season exhibited extreme characteristics.Monthly rainfall was highest in April,followed by June and then May.Cumulative rainfall during the pre-flood season displayed a spatial pattern with the main rain area located in Dongyuan County in the central re-gion,decreasing toward the northern and southern parts.The primary rain area also showed phased spatial variations across different months.Water vapor transported to Heyuan during this period originated mainly from the western Pacific via the South China Sea and the East China Sea,with the South China Sea pathway accounting for the highest proportion(92.03％).Two airflows-one from the Bay of Bengal and the other from the western Pacific-converged over Guangdong.Before the monsoon onset(April),the water vapor flux was significantly stronger than during the transition period and after the monsoon onset(May-June).Varia-tions in the direction and intensity of monthly water vapor transport played a regulatory role in the cumulative rainfall and the positioning of the main rain area in Heyuan.