| 2019年8月16日沈阳极端降水事件的低空γ中尺度涡旋观测特征和机理分析 |
| |
| 引用本文： | 杨磊,郑永光,袁子鹏,袁潮,蒋超,陈宇.2019年8月16日沈阳极端降水事件的低空γ中尺度涡旋观测特征和机理分析[J].气象学报,2023,81(1):19-39. |
| |
| 作者姓名： | 杨磊 郑永光 袁子鹏 袁潮 蒋超 陈宇 |
| |
| 作者单位： | 1.辽宁省气象灾害监测预警中心，沈阳，110166 |
| |
| 基金项目： | 国家重点研发计划重大专项（2018YFC1507301）、中国气象局重点创新团队（CMA2022ZD07）、中国气象局创新发展专项（CXFZ2022J059）、中国气象局预报员专项（CMAYBY2017015、CMAYBY2020026）、风云卫星应用先行计划（FY-APP-2021.0114）、环渤海区域科技创新项目（QYXM202001、QYXM 202102）、国家自然科学基金项目（41705127） |
| |
| 摘 要： | 2019年8月16日沈阳市区受伴有低空γ中尺度涡旋的强对流系统影响，发生了1951年有观测记录以来的最大小时降水（102 mm）。为了提高对此类涡旋所致强降水天气的认识和预报能力，综合利用多源观测和ERA5再分析资料，对此次过程中低空γ中尺度涡旋的观测特征、形成原因和对强降水的影响机制开展研究。此次过程期间，500 hPa沈阳位于东北冷涡东南侧，850 hPa以下低空位于“利奇马”台风残涡西侧的偏北气流水汽输送带内，16日午后沈阳市区具有低层大气气温廓线接近干绝热递减率、较低抬升凝结高度和逐渐加强的风垂直切变等环境条件特征；风廓线雷达资料显示降水前0—6 km风矢量差最大达17 m/s，有利于较浅薄中尺度涡旋对发生。16时前后，沈阳市区内γ中尺度辐合风场首先触发局地风暴，随后有对流风暴群移入沈阳，在局地风暴具有反气旋式旋转处合并。合并风暴在初期产生强降水后，回波顶降低、降水强度减小，低空出现了生命期约30 min的γ中尺度涡旋对，更是出现罕见的具有辐合特征的反气旋式涡旋加强的现象，伴有低空涡旋的风暴再次加强并导致后期更强的降水。相比中国中气旋统计特征，本次低空浅薄涡旋生命期较短、尺度小...
|
| 关 键 词： | 低空γ中尺度涡旋 极端降水 观测分析 环境背景 |
| 收稿时间： | 2022-02-09 |
| 修稿时间： | 2022-06-30 |
The low-level meso-γ-scale vortices during the extreme rainfall in Shenyang on 16 August 2019: Formatiom,merging, and rain-producing mechanisms |
| |
| Institution: | 1.Liaoning Meteorological Disaster Monitoring and Early Warning Centre，Shenyang 110166，China2.Key Opening Laboratory for Northeast China Cold Vortex Research，Shenyang 110166，China3.National Meteorological Centre，Beijing 100081，China4.Liaoning Provincial Meteorological Bureau，Shenyang 110001，China |
| |
| Abstract: | The urban area of Shenyang was affected by an intense rainfall system with low-level meso-γ-scale vortices on 16 August 2019. This system caused record-breaking hourly precipitation (102 mm) since the observations started in 1951. In order to improve the analysis and forecasting ability of heavy rain caused by such vortices, multi-source observations and ERA5 reanalysis data are comprehensively used to analyze the characteristics of the low-level meso-γ-scale vortices in this process, the environment for their generation and their roles in the formation of the torrential rain. The results show that during this process, Shenyang was located in the front of the Northeast Cold Vortex at 500 hPa and in the water vapor conveyor belt on the west side of the residual vortex of typhoon "Likima" at low levels. Moreover, a low-level nearly dry adiabatic lapse rate prevailed in the urban area of Shenyang on the afternoon of 16 August with lower lifted condensation level and increasing vertical wind shear. At 16:00 BT (Beijing Time), the meso-γ-scale convergent wind field in the urban area of Shenyang triggered the local storm, and the cold vortex storm then entered Shenyang. The storm group merged in the area with anticyclonic rotation of the local storm. The merged storm strengthened precipitation, and a meso-γ-scale vortex pair with a lifetime of 30 min appeared in lower levels, followed by a rare phenomenon of the strengthening of the converging anticyclonic vortex. Compared with the statistical characteristics of mesocyclones in China, this low-level shallow vortex demonstrated a short life span with small scale, slow moving speed and strong vertical vorticity. All the automatic weather stations with precipitation exceeding 10 mm in 5 min after the vortex were located in the area between the vortex pair, and the record-breaking intense hourly precipitation occurred since observations started in 1951. The strength and extent of the heavy precipitation can be characterized by the strength of the vortex's rotation, the height of its extension, and the distance between the two vortices. The occurrence of extreme precipitation events requires strong rainfall intensity and long duration time. The merged storm in this process had the characteristics of warm clouds and low centroid echo in radar observations. The early local storm precipitation also reduced the difference between ground temperature and dew point, which ensured high precipitation efficiency. Furthermore, the updraft near the ground generated by low-level vortex promoted the growth and collision of raindrops, thereby enhanced the rain intensity. The strong rotation of the vortex caused an updraft near the ground, which was conducive to the re-development of storms and prolonged the precipitation duration time. The reason for the emergence and strengthening of the low-level anticyclonic vortex is likely attributed to the following factors. The low-level quasi-linear outflow boundary of the cold vortex storm formed a horizontal vortex tube from north to south. Under the downward twisting action of the downdraft in the initial precipitation, meso-γ-scale vortex pair appeared near the ground, and since the environmental wind shear vectors rotated counterclockwise with altitude, the clockwise rotation was more conducive to the strengthening of anticyclonic storms. This is consistent with the theoretical research. In addition, this anticyclone was closer to the strong updraft area in the merged storm, and it could also be reinforced under its stretching. Finally, the formation mechanism of this low-level meso-γ-scale vortices and the rainstorm model are summarized, which provide a reference for future weather analysis and forecasting research. |
| |
| Keywords: | |
|
| 点击此处可从《气象学报》浏览原始摘要信息 |
| 点击此处可从《气象学报》下载免费的PDF全文 |
|
