云贵高原东侧两次强对流天气差异对比

Contrast between two severe convections in east Yunnan-Guizhou Plateau

  • 摘要: 2022年和2023年的3月16日午后到3月17日凌晨贵州省均出现了大范围强对流天气,冰雹、大风、短时强降水在2次过程中相伴出现. 利用多源资料对这2次大范围强对流天气的环流形势、大气环境特征、雷达回波和云图演变特征等进行分析. 结果表明:2次强对流天气均为高空槽东移过程中强干冷空气从500 hPa侵入,在地面辐合线的触发下造成;2次过程均有冷池出流自西北向东南移,使得对流发展东移,冷池前沿的地面辐合线附近是主要降雹区域,冷池移动的前沿是雷暴大风发生的主要区域;2次过程的0~6 km风切变(shear of wind from 0 km to 6 km, SHR 6)大于20 m/s、0 ℃层湿球温度(wet blub zero, WBZ)高度在3~4 km、−20 ℃层高度在6~7 km、订正后对流有效位能(convective available potential energy, CAPE)值超过1500 J/kg、整层为上干下湿的“倒喇叭口”型大气不稳定层结分布;700 hPa、850 hPa相对湿度梯度大值区和ΔT700−500、ΔT850−500梯度大值区叠加区可作为冰雹落区预报和预警的指标;2次过程中直径大于20 mm的冰雹均为孤立对流单体产生,且都具有回波悬垂、有界弱回波或弱回波、大于50 dBz的强回波质心特征.

     

    Abstract: Guizhou Province experienced large-scale severe convective weather on March 16th to 17th of both 2022 and 2023, accompanied by hail, strong winds, and short-term heavy precipitation in the two processes. Based on multiple sources of data, the characteristics of circulation, atmospheric environment, radar echo, and cloud image evolution of these two large-scale severe convective weather events were analyzed. The results showed that both the severe convective weather events were caused by the intrusion of strong dry and cold air from 500 hPa during the eastward movement of the upper trough, triggered by the ground convergence line. In both the processes, the outflow of cold pools moved from northwest to southeast, which made the convection develop eastward; the main hail area was near the ground convergence line at the front of the cold pool, and the front end of the cold pool movement was the main area where thunderstorm winds occurred. The SHR6 of the two processes was greater than 20 m/s, the WBZ was at 3−4 km, the −20 ℃ layer was at 6−7 km, the CAPE after correction was more than 1 500 J/kg, the whole layer was an “inverted trumpet” atmospheric junction distribution with dry top and wet bottom, and the atmospheric junctions of both the processes were unstable. The indicators that can be used for the forecast and early warning of hail falling areas are the regions with large relative humidity changes of 700 hPa and 850 hPa and the overlapping regions with large changes of ΔT700-500 and ΔT850-500. The hail larger than 20 mm in the two processes were generated by isolated convection cells, and all had echo overhang, bounded weak echo or weak echo, and strong echo centroid larger than 50 dBz.

     

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