Journal of Arid Meteorology ›› 2022, Vol. 40 ›› Issue (6): 993-1002.DOI: 10.11755/j.issn.1006-7639(2022)-06-0993

• Articles • Previous Articles     Next Articles

Environmental conditions and mesoscale characteristics of severe convective weather in Beijing-Tianjin-Hebei on 5 July 2021

XU Min1,2(), SHEN Fang2, LIU Xuan3, LIU Yanjie2, ZHANG Xianghan2   

  1. 1. Key Laboratory of Meteorology and Ecological Environment of Hebei Province, Shijiazhuang 050021, China
    2. Langfang Meteorological Bureau of Hebei Province, Langfang 065000, Hebei, China
    3. Wen’an County Meteorological Bureau of Hebei Province, Wen’an 065800, Hebei, China
  • Received:2022-01-12 Revised:2022-04-02 Online:2022-12-31 Published:2023-01-10

京津冀“7·5”强对流天气形成的环境条件及中尺度特征

许敏1,2(), 沈芳2, 刘璇3, 刘艳杰2, 张湘涵2   

  1. 1.河北省气象与生态环境重点实验室,河北 石家庄 050021
    2.河北省廊坊市气象局,河北 廊坊 065000
    3.河北省文安县气象局,河北 文安 065800
  • 作者简介:许敏(1983—),女,高级工程师,主要从事天气预报与决策服务工作.E-mail: hblfxm@163.com
  • 基金资助:
    河北省气象局面上项目(21ky21);河北省科技厅重点研发计划项目(20375407D);廊坊市气象局科研项目(2021-13)

Abstract:

From the afternoon to night on 5 July 2021, severe convective weather including short-time heavy precipitation, thunderstorm wind and small hail occurred in the central region of Beijing-Tianjin-Hebei. The atmospheric environmental conditions and mesoscale characteristics of the formation of this weather process were analyzed by using the data of egional automatic meteorological station, Doppler radar, FY-2G meteorological satellite and microwave radiometer, and the fifth generation atmospheric reanalysis ERA5 from European Centre for Medium-Range Weather Forecasts. The results show that favourable water vapor conditions appeared before the occurrence of the severe convective weather including heavy precipitation, thunderstorm winds and local hail. Strong convergence of water vapor fluxes in lower and middle layers occurred 1 to 2 hours earlier than precipitation. The whole layer atmospheric precipitable water had accumulated continuously under strong uplift. The heat and power unstable environment of severe convection breaking out was created by formation of vertical θse energy frontal zone, maintenance of "upper dry and lower wet" unstable stratification, establishment of strong vertical wind shear from 0 to 6 km and enhancement of CAPE, K and SI indexes. Unstable stratification formed by eastward movement of the upper though carrying dry and cold air southward and low warm tongue, which had provided synoptic-scale upward movement for the occurrence of severe convection. The strong convective happening released more energy in the afternoon than in the evening. Heavy rainfall caused the local temperature to drop significantly and cold pool effect was more significant, which corresponded to the heavy precipitation area during the southward movement process. The surface convergence line at the cold pool boundary was the mesoscale trigger system. The cloud base height dropped and infrared brightness temperature increased rapidly, which indicated the formation of strong convective cloud cluster. The clear shadow at the southeast boundary of cloud body indicated the strong development of cumulonimbus cloud. Under the background of large-scale weather system, the important characteristic indexes obtained from in-depth analysis of mesoscale system can be used for the short term forecast and warning of severe convective weather.

Key words: strong convection, mesoscale characteristics, cold pool, ground convergence line

摘要:

2021年7月5日下午至夜间,京津冀中部地区陆续出现短时强降水、雷暴大风、小冰雹等混合型强对流天气,基于地面区域自动气象站、多普勒雷达、FY-2G气象卫星、微波辐射计以及欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析资料ERA5等多源资料,重点对此次短时强降水形成的大气环境条件和中尺度特征进行探讨分析。结果表明:此次短时强降水、雷暴大风和局地小冰雹的混合型强对流天气发生前即显现出良好的水汽条件,低层和中层的水汽通量强辐合早于降水1~2 h出现,整层大气可降水量在强抬升作用下不断累积;垂直假相当位温(θse)能量锋区的形成,“上干下湿”不稳定层结的维持,0~6 km强垂直风切变以及对流有效位能(convective available potential energy,CAPE)、K指数、SI增强等条件的建立,为强对流的爆发创造了热力、动力和不稳定环境;高空槽东移携带干冷空气南下与低空暖舌共同形成的不稳定层结,为强对流天气的出现提供了天气尺度上升运动;下午时段出现的强对流较夜间能量释放更大,高强度的降水导致局地气温骤降,冷池效应更明显,其南移过程中与强降水落区对应,冷池边界的地面辐合线为中尺度触发系统;云底高度迅速下降、云底红外亮温骤增预示着强对流云团形成,云体东南边界清晰的暗影表明积雨云强烈发展。大尺度天气系统背景下,对中尺度系统深入分析得到的重要特征可用于强对流天气的短临预报预警。

关键词: 强对流, 中尺度特征, 冷池, 地面辐合线

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