大连地区一次副热带高压边缘暖锋暴雨机制分析  

Mechanism Analysis of a Warm Front Rainstorm Event at the Edge of Subtropical High in Dalian

作　　者：王秀萍 赛瀚 刘晓初 李燕 WANG Xiuping;SAI Han;LIU Xiaochu;LI Yan(Institute of Atmospheric Environment,China Meteorological Administration,Shenyang 110166,China;Dalian Meteorological Observatory,Dalian 116001,China)

机构地区：[1]中国气象局沈阳大气环境研究所,辽宁沈阳110166 [2]大连市气象台,辽宁大连116001

出　　处：《沙漠与绿洲气象》2023年第4期16-23,共8页Desert and Oasis Meteorology

基　　金：中国气象局沈阳大气环境研究所联合开放基金课题面上基金项目(2021SYIAEKFMS04)。

摘　　要：利用常规气象观测资料、自动站逐时降雨量资料以及NCEP逐6 h再分析资料(1°×1°),对2020年8月31日大连地区一次副热带高压(简称“副高”)边缘暖锋暴雨过程的环境场特征和动力、热力机制进行分析。结果表明:暴雨发生在远距离台风活动的有利背景下,由副高、500 h Pa高空槽和850 hPa暖式切变线共同影响所致。大连地区处于副高边缘,台风造成副高西伸北抬,副高和台风外围的偏南暖湿气流共同为暴雨区输送充足的水汽条件,为此次暴雨的产生提供了有利的大尺度环流背景场。暴雨发生前大气对流不稳定,深厚的湿层和暖云层以及较低的云底高度,是产生较高降雨效率的有利条件。850 hPa比湿>14 g/kg,超过区域暴雨阈值;近地层出现强水汽通量辐合中心并配合上升运动区,对强降水的预报具有明显指示意义。高空急流提供强辐散“抽吸”作用,对流层中下层西南风的不断加强和向下传播出现低空和超低空急流,高、低空急流耦合形成较强的上升运动,触发不稳定能量释放,产生强降水。超低空急流的出现对此次暴雨的产生、发展和维持发挥关键的作用。暴雨区上空存在广义位温等值线密集带和陡立区,由于凝结潜热释放而引起广义位温高值区呈漏斗状向下伸展,中低层强暖平流促使湿斜压性显著增强,有利于暖锋锋生,从而导致整层饱和大气的抬升,最终产生强降雨天气。Based on conventional meteorological observations,hourly observational precipitation data from regional automatic weather stations,and NCEP 6-hour reanalysis data(1 ° × 1 °),this study analyzed the environmental field characteristics,dynamic mechanisms,and thermal mechanisms of a warm frontogenesis rainstorm process at the edge of the subtropical high that occurred on August 31,2020 in the Dalian area.The results show that this rainstorm event occurred in the favorable context of long-distance typhoon activity.And the subtropical high,an upper trough at 500 hPa,and a warm shear line at 850 hPa,jointly contributed to the development of the rainstorm.Dalian was located on the north edge of the subtropical high pressure,and the typhoon caused the subtropical highs to stretch westward and northward.The warm and moist southerly airflow associated with the subtropical high and outer circulation of the typhoon provided a favorable large-scale circulation background for the rainstorm.Prior to the initiation of rainstorms,convective instability,thicker warm and moist layer,and lower cloud base were favorable conditions for high precipitation efficiency.The specific humidity of 850 hPa was greater than 14 g/kg,which exceeded the regional rainstorm threshold.A strong water vapor flux convergence center appeared near ground level,overlapping with the ascending area,indicating probable heavy precipitation.A high-level jet stream provided strong divergence,and the southwest jet streams of the lower and middle troposphere enhanced constantly and propagated downward,leading to the occurrence of a low-level jet stream and ultra-low-level jet streams.The coupling of the upper and lower-level jets formed a strong upward motion,triggering the release of unstable energy and producing heavy precipitation.The appearance of ultra-low-level jets played a key role in the initiation,development,and persistence of rainstorms.Dense zones of generalized potential temperature contour lines and steep areas existed over the rainstorm area.Due

关 键 词：暴雨 对流不稳定 超低空急流 广义位温 暖锋锋生 

分 类 号：P458.121.1[天文地球—大气科学及气象学]