Analysis of the Anomalous Characteristics and Causes of Pre-flood Season Precipitation in Guangdong in 2024

WANG Mingsheng; HU Ting; HU Yamin; DU Hui; DONG Shaorou

doi:10.3969/j.issn.1007-6190.2025.05.001

Abstract：Based on NCEP/NCAR reanalysis data and conventional meteorological observation data,this study employs mathematical and statistical methods to analyze the anomalous characteristics of precipita-tion and their causes during the pre-flood season(April to June)in Guangdong in 2024.The results show that the flood season in Guangdong started earlier in 2024.The total pre-flood season rainfall was 52%more than normal,reaching a record high for the same period.The number of precipitation days increased by 11.2 days,with the precipitation exhibiting pronounced intraseasonal variation.Early-stage sea surface tem-perature changes and concurrent atmospheric circulation patterns significantly influenced the abnormally high precipitation.The moderate-strength El Niño event that started in May 2023 peaked in winter and then en-tered a decay phase.Associated sea surface temperatures in the tropical Indian Ocean and the North Atlantic Ocean were historically high during winter and maintained an anomalously warm trend into spring.Affected by the El Niño event,an anomalous anticyclonic circulation developed over the Philippines.Under the com-bined effects of the Philippine anticyclone and tropical Indian Ocean warming,the Western Pacific Subtropi-cal High during the pre-flood season showed abnormally strong intensity and an anomalously westward-exten-ding ridge point.Located on the northern flank of the subtropical high,Guangdong experienced continuous moisture transport from the South China Sea and the northern Bay of Bengal.Coupled with active plateau troughs and southern branch troughs,these conditions led to frequent heavy precipitation processes during the pre-flood season in Guangdong,characterized by prolonged duration,abnormally high cumulative rain-fall,and high precipitation intensity.