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气象:2022,48(6):719-728
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冷涡底部对流引起的杭州湾极端大风形成机制分析
彭霞云,章丽娜,刘汉华,李文娟,黄新晴,黄旋旋
(浙江省气象台,杭州 310051;中国气象局气象干部培训学院,北京 100081)
Formation Mechanism of Extreme Winds in Hangzhou Bay Caused by Convection at the Bottom of Cold Vortex
PENG Xiayun,ZHANG Lina,LIU Hanhua,LI Wenjuan,HUANG Xinqing,HUANG Xuanxuan
(Zhejiang Meteorological Observatory, Hangzhou 310051;China Meteorological Administration Training Centre, Beijing 100081)
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投稿时间:2021-03-20    修订日期:2022-05-04
中文摘要: 2020年4月12日,受冷涡影响,华东地区出现了大范围的雷暴大风,其中在杭州湾地区出现了12级以上的极端大风。此次强对流过程发生前,高低空为一致的西北气流,水汽含量低、能量条件弱,预报难度大,沿海海面风力预报出现了较大的偏差。基于常规观测资料及多普勒天气雷达、风廓线雷达等非常规观测资料,结合ERA5再分析资料,分析了此次过程雷暴大风特征及对流系统移入杭州湾前后的演变特征,重点探讨了杭州湾东北部出现极端大风的可能原因。研究表明,杭州湾极端大风的形成是多因素共同作用的结果。杭州湾具有一定的能量条件、低层大气的温度直减率接近干绝热递减率,有利于对流系统中形成较强的下沉气流,下沉辐散造成地面大风。中层存在西北风急流,在对流下沉运动的作用下,中层的高动量被带到地面,增强了地面风速。对流系统移入杭州湾的过程中,冷池增强,而杭州湾水面的摩擦力比陆地小,有利于风速增强,这也是杭州湾风力增强的重要原因之一。杭州湾东北部13级以上大风的出现还与海上热力、动力条件的不均匀分布及对流入海后形态的变化有关。
Abstract:On April 12, 2020, affected by the cold vortex, a large-scale thunderstorm and gale occurred in East China, including an extreme gale exceeding the Beaufort scale 12 in Hangzhou Bay. Before the occurrence of this severe convection process, the high and low levels had consistent northwest air flow, with low water vapor content and weak energy conditions, so it was difficult to predict, thus larger deviations appeared in coastal sea surface wind forecast. Based on conventional observation data and Doppler weather radar and wind profile radar data, combined with ERA5 reanalysis data, this paper analyzes the characteristics of thunderstorm gale in this process and the evolution characteristics of convective system before and after its moving into Hangzhou Bay, and focuses on the possible causes of extreme gale in the northeast of Hangzhou Bay. The research shows that the formation of extremely strong wind in Hangzhou Bay was the result of the joint action of many factors. Hangzhou Bay had certain energy conditions, and the temperature reduction rate of the lower atmosphere was close to the dry adiabatic decline rate, which was conducive to the formation of strong downdraft in the convective system and the surface strong wind caused by subsidence divergence. There was a northwest wind jet in the middle layer. Under the action of convective subsidence, the high momentum in the middle layer was brought to the ground, enhancing the ground wind speed. During the process of the convective system moving towards Hangzhou Bay, the cold pool enhanced, and the friction on the water surface of Hangzhou Bay was smaller than that on land. Therefore, the intense flow in the cold pool spread faster, which was also one of the important reasons for the increasing of wind speed in Hangzhou Bay. The occurrence of gales above Beaufort scale 13 in the northeast of Hangzhou Bay was also related to the uneven distribution of marine thermal and dynamic conditions and the variation of echo shape after the convection moved into the sea.
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基金项目:浙江省科技厅科技项目(2022C03150)、中国气象局创新发展专项(CXFZ2021Z033)和华东区域气象科技协同创新基金(QYHZ202111)共同资助
引用文本:
彭霞云,章丽娜,刘汉华,李文娟,黄新晴,黄旋旋,2022.冷涡底部对流引起的杭州湾极端大风形成机制分析[J].气象,48(6):719-728.
PENG Xiayun,ZHANG Lina,LIU Hanhua,LI Wenjuan,HUANG Xinqing,HUANG Xuanxuan,2022.Formation Mechanism of Extreme Winds in Hangzhou Bay Caused by Convection at the Bottom of Cold Vortex[J].Meteor Mon,48(6):719-728.