基于区域自动站的东莞极端短时强降水特征

Characteristics of Extreme Short⁃range Intense Rain in Dongguan Based on the Data of Regional Automatic Weather Stations

选取2008—2019年东莞地区97个区域气象站的逐小时降水观测资料,统计分析了东莞极端短时强降水的特征,结果表明:东莞地区极端短时强降水总体呈现出中西部多、东部少的特征。城区片是极端短时强降水的易发区域,说明城市作用对稳定滞缓的降水系统有阻碍效应,导致城区的降水强度增大。全市极端短时强降水总体大致呈现“一年多两年少”的波动上升趋势;年内分布主要集中在主汛期(4—9月),并在5—6、8月呈现出“双峰”特征;午后到傍晚、凌晨到早晨是极端短时强降水的易发时段。小时雨量在50~59.9 mm范围内出现的次数最多,占比超50%;小时雨量在100 mm以上出现过28次;极端短时强降水年极值在5—6月出现次数最多,2010年5月7日出现极端最强短时强降水,为143 mm。极端短时强降水年极值事件的天气流型配置主要有西南气流型、冷空气切变型、季风低压型和东风波型4种;发生在前汛期的主要影响系统为西南气流型和冷空气切变型,发生在后汛期的则为季风低压型和东风波型。

Using hourly rainfall observations from 97 regional automatic weather stations of the Dong⁃guan area from 2008 to 2019,this work runs a statistical analysis of the characteristics of extreme short⁃range intense rains(to be abbreviated as“ESI⁃Rain”hereafter)in Dongguan.The results are shown as follows.Generally,the ESI⁃Rain is more in the central and western part than in the eastern part of Dongguan and the urban districts are the highly likely locations for it to happen.It suggests that the urban effect blocks raining systems that are stable and stagnating,increasing the rain intensity there.In general,the city's ESI⁃Rain in⁃creases in a fluctuating pattern that marks a rising year followed by two declining years.It mainly occurs in the primary flood season(April to September)and is bimodal with a peak in May and June and the other in August.The time from midday to evening and across the sunrise are mostly likely to have the ESI⁃Rain.Hourly rainfall amount is mostly between 50 and 59.9 mm,taking up more than 50%of the total,with 28 processes surpassing 100 mm.Annual extremes of the ESI⁃Rain take place most frequently in May and June,with the most extreme case appearing on May 7,2010(143 mm).Synoptic flow patterns associated with the ESI⁃Rain include the southwesterly airflow,cold air shear,monsoonal low and the easterly wave,with the former two patterns being the main governing systems for the April to June flood season and the latter two for the July to September flood season.