摘要: |
利用地面自动站资料、探空资料、多普勒雷达观测资料以及ERA5逐时再分析资料对2021年5月15日发生在黔北的一次下击暴流事件成因及雷达回波特征进行分析。结果表明:(1)本次过程发生在500hPa槽前、西南低涡南侧、中低空急流北侧和地面锋前热低压内的大范围上升区内,地面辐合线是重要的触发机制。(2)大气为上干下湿不稳定状态,中等到强的垂直风切变维持,环境温度垂直递减率较大,低层有冷空气入侵,下沉气流接地时与周围大气形成10℃以上的温差,导致气流强烈辐散最终产生大风。(3)过程由多单体风暴引发,具有弓形回波、三体散射长钉、回波悬垂等结构特征,回波核强度在65dBz以上,大风出现时强回波核迅速降落。(4)大风发生前,风暴前侧有一支由前向后的斜升气流与后侧入流气流形成中层径向辐合(MARC),大风出现时,低层有小尺度辐散区域,随后辐散尺度扩大,风速切变减小,大风强度减弱。 |
关键词: 下击暴流;上干下湿;弓形回波;中层径向辐合 |
DOI: |
投稿时间:2022-12-09修订日期:2023-05-05 |
基金项目: |
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Analysis of the causes and radar echo characteristics of adownburst event occurred in northern Guizhou |
LI Xia,ZHANG Yunqiu,LIU Hongshuang,TANG Hai,YANG Yi |
(Zunyi Meteorological Observatory) |
Abstract: |
Based on the automatic station data、upper-air observation data、Doppler radar observation data and ERA5 hourly reanalysis data,the causes and radar echo characteristics of a downburst event occurred in northern Guizhou on 15 May,2021 was analyzed.The results are as follows:(1)This process occurs within a broad upwelling zone in front of a 500hPa trough, at the south of a southwest low vortex,and the north of a mid- to low-level rapid, within a surface frontal thermal low pressure, with surface convergence lines being an important trigger mechanism.(2)The atmosphere is in an unstable state of dryness above and wetness below, with moderate to strong vertical wind shear maintained, a large vertical rate of decrease in ambient temperature, cold air intrusion at lower levels, and a temperature difference of more than 10°C between the sinking airflow and the surrounding atmosphere when the ground is formed, resulting in strong dispersion of airflow eventually producing gale force winds.(3)The process is triggered by multi-monomer storms, with structural features such as bow echoes, three-body scattering long spikes, and echo overhangs, with echo nuclei of 65 dBz or more in strength, and strong echo nuclei landing rapidly when high winds appear.(4)Before the occurrence of gale, there is an oblique updraft from the front side of the storm and the back side of the incoming airflow to form a mid-level radial convergence (MARC), when the gale appears, there is a small-scale dispersion area at the lower level, and then the dispersion scale expands, the wind speed shear decreases, and the intensity of the gale weakens. |
Key words: downburst; Dry on top and wet at the bottom; Bowed Echo; mid-level radial convergence |