青海海南一次短时强降水天气过程成因分析

Cause Analysis of a Short-term Heavy Precipitation Process in Hainan,Qinghai

利用常规高低空观测资料、雷达资料及ERA5再分析资料,对2022年8月9日青海海南短时强降水天气过程成因进行分析。结果表明:(1)此次过程的特点是强度强,站点分散。(2)过程发生于南亚高压控制区域内,强降水发生在200 hPa高空急流右侧,配合500 hPa副热带高压北伸、700 hPa低压系统及地面辐合线,垂直运动旺盛;500 hPa湿区叠置于地面显著湿区上空,过程水汽充沛。地面中尺度辐合线与干线是此次过程的触发机制。(3)从物理量及探空资料分析,台风“木兰”北部偏东气流为高原东部提供水汽输送,探空可见湿层深厚,上干下湿,层结不稳定,满足对流天气发生的水汽条件及不稳定层结条件。垂直运动深厚,较强的动力抬升有利于低层暖湿空气在垂直方向的输送。并且垂直速度和散度随时间的变化与短时强降水的起始时间有较好的对应关系。(4)从雷达回波可见此次为暖云主导型的对流降水。对流云系长期维持造成了共和、兴海、贵南区域的短时强降水,而贵德区域短强则是因为云系不断经过形成“列车效应”。径向速度均存在明显的低层辐合、高层辐散的配置。分析结果对提高海南地区短临预报时效和预报预警的准确度具有重要的参考意义。

This paper analyzed the causes of short-term heavy precipitation weather process in Hainan,Qinghai Province on August 9,2022 by conventional high and low altitude observation data,radar data and ERA5 reanalysis data.The results show that:(1)The process is characterized by strong intensity and scattered stations.(2)The process occurred in the area controlled by the South Asian high,and the heavy precipitation occurred on the right side of the 200 hPa upper jet stream,with the northward extension of the 500 hPa subtropical high,the 700 hPa low pressure system and the surface convergence line,and the vertical movement was vigorous.The 500 hPa wet zone is overlapped over the significant wet zone on the ground,and there is abundant water vapor in the process.The surface mesoscale convergence line and trunk line are the trigger mechanism of this process.(3)From the analysis of physical quantities and sounding data,the easterly airflow in the north of Typhoon“Mulan”provides water vapor transport for the eastern part of the plateau.Sounding shows that the wet layer is deep,dry at the top and wet at the bottom,and the stratification is unstable,which meets the water vapor conditions and unstable stratification conditions of convective weather.The vertical motion is deep,and the strong dynamic uplift is beneficial to the vertical transportation of warm and humid air in the lower layer.And the variation of vertical velocity and divergence with time has a good corresponding relationship with the start time of short-term heavy precipitation.(4)From radar echoes,it can be seen that this convective precipitation is dominated by warm clouds.The long-term maintenance of convective cloud system has caused short-term heavy precipitation in Gonghe,Xinghai and Guinan regions,while the short-term strength in Guide region is due to the“train effect”formed by the continuous passage of cloud system.There is obvious convergence in the lower layer and divergence in the upper layer of radial velocity.The analysis results have important reference significance for improving the timeliness of short-term and impending forecasting and the accuracy of forecasting and early warning in Hainan area.