江西副高边缘雷暴大风雷达拼图回波特征分析

Analysis of characteristics of mesoscale thunderstorm gale echo on the edge of subtropical high

摘要:

利用MICAPS常规天气图资料、地面自动气象站资料、雷电资料和雷达拼图等资料，采用天气图中分析方法、统计方法、回波图像、回波廓线等分析方法，对2020年7月11日江西副热带高压边缘中尺度雷暴大风回波特征进行分析，结果表明：1）副热带高压控制或边缘上，江西上空100 hPa是东北风，500 hPa是西南风，高空呈现逆时针环流，T-lnP图上层结不稳定，对流有效位能CAPE （Convective Available Potential Energy）面积较大，对产生强对流天气有利；由于上下两层的风向不同，使得雷暴回波系统的移动与回波系统的云砧伸展方向不一致，从而加剧了对流上升运动，使得雷暴回波系统发展、加强、维持。2）回波产生初期是局地对流单体回波，通过不断新生单体和单体合并等方式，形成南北走向的回波短带，这种合并形成的回波短带发展旺盛时，会产生多站雷暴大风天气。3）南北走向的回波短带是产生雷暴大风的主要回波特征，虽然回波强度只有55 dBZ，但移动速度较快（60～70 km/h），造成地面大风。江西WebGIS雷达拼图上叠加多部雷达风暴跟踪信息STI （Storm Tracking Information），可以明确风暴的移动方向和移动速度，根据STI密集区判断，增加了STI的可用性。4）“前伸”或“延伸”回波反映了回波系统上方的高空风走向和积雨云的云砧飘离方向。“延伸”回波一定程度上表现出副高边缘雷暴回波系统的强弱程度。为改进副热带高压边缘中尺度雷暴大风的预警预报准确率提供依据。

关键词:江西;副热带高压;雷暴大风;雷达拼图回波特征;延伸回波

Abstract:

The echo characteristics of Jiangxi subtropical high edge mesoscale thunderstorm gale on July 11, 2020 were examined using MICAPS conventional weather map data, ground automatic weather station data, lightning data and radar mosaic data, for the study of weather evolution and radar mosaic echo characteristics.The results show that:1) under the control or edge of subtropical high, the northeast wind is at 100 hPa and the southwest wind is at 500 hPa over Jiangxi, and the upper layer of T-lnP is unstable and CAPE area is large, which is beneficial to strong convective weather;Because of the different wind directions on the upper and lower floors, the movement of thunderstorm echo system is inconsistent with the extension direction of cloud anvil of echo system, which intensifies the convection rising movement and makes thunderstorm echo system develop, strengthen and maintain.2) At the initial stage of echo generation, it is the local convection single echo, and the echo short band in the north-south direction is formed by using the new generation and a single combination.As the echo short band forms vigorously, it will produce thunderstorms with multiple stations and windy weather.3) The main echo feature of a thunderstorm gale is the short echo band in the north-south direction.Despite the low echo intensity of 55 dBZ (60-70 km), the echo travels at speed, resulting in the gale.The multiple radar storm tracking information STI (Storm Tracking Information) is superimposed on Jiangxi WebGIS radar mosaic, which can clearly show the moving direction and speed of storms, and will be more useful if STI dense areas are used.4) The "forward" or "extended" echo reflects the high-altitude wind direction over the echo system and the cloud anvil drifting away from cumulonimbus clouds.In some ways, the "extended" echo shows the strength of the thunderstorm echo system at the edge of the subtropical high.It provides a basis for improving the early forecasting and early warning of mesoscale thunderstorm gales at the edge of subtropical highs.

Key words:Jiangxi;subtropical high;thunderstorms and strong winds;echo characteristics of radar mosaic;extended echo