青海省东南部一次短时强降水成因分析

Analysis of the Cause of a Short-term Heavy Precipitation in the Southeast of Qinghai Province

利用MICAPS系统对发生在2021年8月18日青海省黄南州河南县赛尔龙乡测站短时强降水天气过程前后时段的高低空观测资料、卫星云图产品和测站周边地形等进行分析,结果表明:北支短波槽东移过境触发了此次短时强降水,切变前部西南暖湿气流为其提供了充沛的水汽;地面热低压切变辐合为此次降水创造了有利的热力和动力条件,并提供了一定量的水汽;当地的地形呈西高东低且自东向西呈喇叭口的特征,对入境暖湿空具有强迫辐合抬升作用,有利于降水加强,特殊的地形地貌特征是该地区易产生大降水(短强)的主要因素之一;云图分析表明发展旺盛的强对流单体造成了此次短时强降水;08时探空资料中各项物理指数表明在探空站周边具备发生强对流天气的动力条件和热力条件,这些物理指标对探空站周边发生强对流天气具有很好的指示意义,当各项物理指数大多数满足强对流发生条件时,结合地区降水特征、地形等因素,可以提前预判某些易发强对流天气的地区有可能出现短时强降水;各类数值预报产品对降水过程范围和时段预报具有较好的参考意义,分析结果可为未来类似短时强降水的预报提供参考依据。

Using MICAPS system,high and low altitude observation data,satellite cloud image products and the topography around the observation station(X5007)of Saierlong Township,Henan County,Huangnan Tibetan Autonomous Prefecture,Qinghai Province,before and after the short-term heavy precipitation on August 18,2021 were analyzed.The results showed that the eastward movement of the North Branch shortwave trough triggered the short-term heavy precipitation,and the southwest warm and humid air flow before the shear providing it with abundant water vapor.The surface thermal low-pressure shear convergence created favorable thermal and dynamic conditions for the precipitation,and provided a certain amount of water vapor.It has the effect of forced convergence and uplift to warm and humid air,which is favorable to precipitation enhancement.The special landform is one of the main factors to produce heavy precipitation(short strong)in this area.The analysis of cloud image showed that the strong convective cells caused the short-term heavy precipitation.The physical indexes in the sounding data at 8 am showed that there were dynamic and thermal conditions for the strong convective weather around the sounding station,when most of the physical indexes satisfy the condition of strong convection,the regional precipitation characteristics,topography and other factors should be taken into account.It is possible to predict in advance the possibility of short-term heavy precipitation in some regions prone to strong convective weather,and various numerical forecast products have good reference significance for the range and time of precipitation process.