强弱天气尺度强迫下广东短时强降水时空特征分析

SPATIAL AND TEMPORAL CHARACTERISTICS OF SHORT-TERM HEAVY RAINFALL IN GUANGDONG UNDER STRONG AND WEAK SYNOPTIC-SCALE FORCING

关键词:  短时强降水  时空分布特征  频次  强天气尺度强迫  弱天气尺度强迫

Key words:  short-term heavy rainfall  spatial and temporal distribution characteristic  frequency  strong synoptic-scale forcing  weak synoptic-scale forcing

摘要:

利用2010—2019年广东区域自动站逐时雨量定义短时强降水日，采用500 hPa和700 hPa广东区域日平均垂直速度来客观衡量天气尺度强迫，并对年均和强/弱天气尺度强迫下的短时强降水进行时空分布特征分析，结果表明：广东区域的短时强降水主要发生在4—9月，发生频次具有准双峰的日变化；粤西是短时强降水最频发区；茂名山区的短时强降水主要发生在白天，弱天气尺度强迫下占比达80%以上；频发次中心位于珠江三角洲，持续1小时以上的短时强降水占该地发生频次75%。强天气尺度强迫下短时强降水4—6月最多，弱天气尺度强迫下则7月达到峰值。弱天气尺度强迫下，仅历时1小时的短时强降水在粤北河源-梅州北部山区、粤东莲花山脉附近有次中心；历时2小时及以上的相对集中在粤西、珠江三角洲北部和粤东惠州-汕尾一带；3月肇庆-云浮和珠江口附近弱天气尺度个例占比高；7月粤北占比高；早晨07时在粤西阳江沿海有孤立的高频中心。

Abstract:

Hourly rainfall data from automatic stations in Guangdong Province during 2010-2019 were used to define short-term heavy rainfall days. The daily mean vertical velocity at 500 hPa and 700 hPa in Guangdong was used to objectively measure the intensity of synoptic-scale forcing. Then the spatial and temporal characteristics of two types of short-term heavy rainfall were analyzed. The results showed that the short-term heavy rainfall in Guangdong mainly occurred from April to September, and the diurnal variation frequency was quasi-bimodal. The west of Guangdong was the area with the most frequent short-term heavy rainfall, and the short-term heavy precipitation in the mountainous area in Maoming mainly occurred in the daytime with 80% under weak synoptic-scale forcing. The center with the second highest frequency was located in the Pearl River Delta, where the short-term heavy rainfall lasting more than one hour accounted for about 75% of the local totals. Under strong synoptic-scale forcing, the short-term heavy rainfall was the most frequent from April to June, while it reached the peak in July under weak synoptic-scale forcing. The highest proportion of short-term heavy rainfall under weak forcing was in Zhaoqing and Yunfu and the Pearl River estuary in March, while in northern Guangdong in July. Under weak forcing, there was an isolated high-frequency center near Yangjiang in the coastal area of western Guangdong at 7:00 am.