华南前汛期珠江流域两类暖区飑线特征分析

Characteristics of two kinds warm-sector squall lines in the Pearl River Basin during the pre-flood season in South China

利用2016—2019年4—6月雷达三维拼图资料,根据触发条件的差异,划分华南前汛期暖区飑线为锋面触发暖区发展(Ⅰ型暖区飑线)与暖区触发并发展(Ⅱ型暖区飑线)两类;在此基础上针对飑线造成短时强降水和雷暴大风的分布,对比了飑线发生时的大尺度环境条件和中尺度雷达回波特征。结果表明:Ⅰ型暖区飑线大多形成于平原地区,Ⅱ型暖区飑线大多生成于山脉迎风坡和海岸线;两类飑线发生时均伴有明显的短时强降水,易造成暴雨洪涝;Ⅰ型暖区飑线易产生区域性雷暴大风,Ⅱ型暖区飑线产生分散性雷暴大风;Ⅰ型暖区飑线生命史长,对流发展更旺盛,飑线移动速度快;Ⅱ型暖区飑线生命史短,飑线移动速度慢,回波强度弱于Ⅰ型暖区飑线;两类飑线都有较好的水汽条件和0~3 km低层风垂直切变条件,Ⅰ型暖区飑线发生时动力和热力条件更好。

Based on the three-dimensional radar mosaic data from April to June in 2016-2019 and the differences in triggering conditions,a classification for warm-sector squall lines with vastly different formation mechanisms during the pre-flood season was proposed.They were divided into two types:squall lines that developed in the warm sector after frontal triggering(Type I warm-sector squall lines),and squall lines that were generated and developed in the warm sector(Type II warm-sector squall lines).On this basis,the distributions of short-term heavy rainfall and thunderstorm winds were compared in terms of large-scale environmental conditions and mesoscale radar echo characteristics during the occurrence of squall lines.The results showed that:Type I warm-sector squall lines were mostly formed in plain areas,while Type II warm-sector squall lines were mostly generated on the windward slopes of mountains and coastlines.Both squall lines were accompanied by obvious short-term heavy precipitation,which was easy to cause rainstorm and flood;Type I warm-sector squall lines were prone to producing regional thunderstorm winds,while Type II warm zone squall lines produce scattered thunderstorm winds.The Type I warm-sector squall lines had longer lifecycle,more vigorous convective development,and a faster moving speed,while the Type II warm-sector squall lines had shorter lifecycle and a slower moving speed with weaker echo intensity.Both types of squall lines had good water vapor conditions and vertical shear conditions of low-level winds at 0-3 km,and the dynamic and thermal conditions are better when Type I warm zone squall lines occurred.