| 川藏高原一次混合型强对流天气的观测特征 |
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| 引用本文： | 王黉,李英,文永仁.川藏高原一次混合型强对流天气的观测特征[J].应用气象学报,2021,32(5):567-579. |
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| 作者姓名： | 王黉 李英 文永仁 |
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| 作者单位： | 1.中国气象科学研究院灾害天气国家重点实验室, 北京 100081 |
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| 摘 要： | 利用中国气象局地面自动气象站、探空、天气雷达等观测资料和ERA-Interim再分析资料，分析2016年9月8日川藏高原一次强对流天气过程。结果表明:该过程多站出现8级雷暴大风、10 mm以上小时强降水且伴有最大直径为18 mm的冰雹，是川藏高原一次混合型强对流过程。对流系统发生在500 hPa弱冷平流和低层切变线影响下，中低层深厚湿层、环境中等强度对流有效位能和垂直风切变为超级单体的形成和维持提供有利条件。初始北侧多单体和南侧弱对流在地面辐合线上生成，向东南移入适宜环境后，北侧多单体发展成线状对流系统，与南侧单体合并且促使其迅速发展成超级单体。成熟超级单体低层具有清晰的前侧入流缺口、钩状回波和中气旋特征。强回波区随高度前倾，呈显著的上冲云顶突起、回波悬垂和有界弱回波区。风暴内中层径向辐合、上升气流减弱和反射率因子核心快速下降预示下击暴流的产生。中层干空气的夹卷和水凝物快速下落的拖曳作用加强下沉气流，结合峡谷地形的狭管效应，引起地面大风。
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| 关 键 词： | 川藏高原 雷暴大风 超级单体 |
| 收稿时间： | 2021-05-21 |
Observational Characteristics of A Hybrid Severe Convective Event in the Sichuan-Tibet Region |
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| Affiliation: | 1.State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences, Beijing 1000812.Ningbo Meteorological Bureau of Zhejiang Province, Ningbo 3510003.Chinese Academy of Meteorological Sciences, Beijing 100081 |
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| Abstract: | The Sichuan-Tibet Region is a key area for the development of western China, where severe convective weather such as thunderstorm gales occur frequently. However, due to the complex terrains, synoptic systems, and the lack of meteorological observations, it is especially challenging to make accurate prediction. To better understand the mechanism of severe convective weather over the plateau, a rare severe convective event in the Sichuan-Tibet Region on 8 Sep 2016 is analyzed with weather reports, hourly and minutely surface observations, sounding data and Doppler weather radar data from China Meteorological Administration and ERA-Interim 0.5°×0.5° reanalysis data from European Centre for Medium-Range Weather Forecasts (ECMWF). The result shows that hourly rainfall of over 10 mm and hails of over 18 mm are observed at several weather stations, indicating a hybrid moist convective event. The meso-scale convective system (MCS) occurs near a shear line at low level with weak cold advection at 500 hPa. Large environmental convective available potential energy (CAPE), vertical wind shear, and the thick moist atmospheric layer are conductive to the formation of supercell. The initial convection is generated along a surface convergence line, with multiple γ meso-scale cells embedded in stratiform cloud in the north and cluster cells in the south. They move to the southeast, enter the favorable environment and merge with each other, enabling the cell on the south side to quickly develop into a supercell. When the supercell grows matured, the characteristic of front inflow gap, hook echoes and mesoscale cyclone at low levels are clear. The strong echo region tilts forward with height. There is significant overshooting top with the echo top height up to 15 km above ground in the upper troposphere, and obvious echo overhang capping bounded weak-echo region (BWER) in the middle layer. Mid-altitude radial convergence, weakening of updrafts and rapid drop of the reflectivity core indicate the occurrence of downbursts inside the storm. The cooling effect due to the entrainment of midlevel dry air is favorable to the growing of big hails and raindrops, and the formation of downdrafts. Moreover, the drag effect related to the rapid drop of heavy raindrops and hails, and the narrow tube effect of the canyon terrain, contribute to the formation of thunderstorm gales near the ground. |
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