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气象:2019,45(1):61-72
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渤海西岸偏东风对天津局地大暴雨的影响分析
尉英华,陈宏,何群英,林晓萌,张辉
(天津市气象台,天津 300074;天津市宝坻区气象局,天津 301800)
Influence of Easterly Winds from West Coast of Bohai Sea on Local Heavy Rainfall in Tianjin
WEI Yinghua,CHEN Hong,HE Qunying,LIN Xiaomeng,ZHANG Hui
(Tianjin Meteorological Observatory, Tianjin 300074;Baodi Meteorological Office of Tianjin, Tianjin 301800)
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投稿时间:2018-02-10    修订日期:2018-08-26
中文摘要: 利用加密自动气象站、多普勒天气雷达和风廓线雷达等高时空分辨率资料,分析2017年7月6日天津一次局地大暴雨过程的中尺度对流系统发展演变特征,讨论渤海西岸边界层偏东风的垂直结构、温湿特性及其对局地大暴雨的作用。结果表明:局地大暴雨由两个暖区中尺度对流系统和一个低涡切变线系统造成,偏东风作用下的暖区第二个中尺度对流系统主导了局地大暴雨的形成。大暴雨中心两侧的温湿特征均呈“东高西低”分布,偏东气流具有暖湿特性,为暖区对流暴雨的发生发展提供了有利的环境条件。由于海陆地形差异,偏东气流自渤海向内陆推进过程中呈现明显的风速扰动特征,不仅导致水汽辐合,同时有利于上升运动发展。其中,0.6 km以下偏东风的中尺度扰动对局地大暴雨的触发和维持起重要作用,风速辐合强迫产生的上升气流是γ中尺度对流单体的重要触发机制,而强降水冷池出流与不断增强的暖湿偏东入流相互作用形成地面中尺度辐合线,使对流系统得以稳定维持,40 dBz以上强降水回波持续近3 h,平均6 min降水量达6.8 mm。此外,局地大暴雨的雨强变化与东风急流波动关系密切,急流的建立、发展、减弱和消失分别对应降水的陡增、峰值、减弱和陡降四个阶段。
Abstract:Based on the high spatio temporal resolution data of automatic weather stations,Doppler weather radar and wind profiler radar, we analyzed the development of the mesoscale convective systems during the heavy rainfall in Tianjin on 6 July 2017, and discussed the structural characteristics of easterly flow from the Bohai Sea and its influence on the local heavy rainfall. The results are as follows: The local heavy rainfall was caused by two warm zone mesoscale convective systems and a vortex shear line system. Among them, the second mesoscale convective system in warm area dominated the formation of local heavy rainfall, and it was closely related to the easterly flow in the boundary layer. The easterly flow during this heavy rainfall had warm and wet characteristics, which was conductive to the occurrence and development of heavy rainstorms. At the same time, the wind speed from the Bohai Sea to the inland showed obviously disturbance, leading to the convergence of water vapor in the boundary layer and the development of the ascending movement. Furthermore, the mesoscale disturbance of easterly flow below 0.6 km played an important role in the triggering and maintaining mechanism of the heavy rainfall. Under the convergence system caused by the wind speed disturbance, the updraft flow was forced, triggering the occurrence of the meso γ scale convection. On the other hand, the outflow of cold pool caused by the heavy rainfall and the increasing easterly inflow interacted each other and formed the convergence, and the meso scale convective system was maintained stably, resulting in the strong precipitation echo above 40 dBz lasting nearly 3 h, with an average precipitation of 6.8 mm per 6 min. In addition, the change of rain intensity was closely related to the fluctuation of the easterly jet in the boundary layer. The establishment, development, weakening and disappearance of the jet corresponded to the four phases of steep increasing, peak, weakening and steep dropping of precipitation.
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基金项目:国家自然科学基金项目(41575049)、天津市自然科学基金项目(16JQNJC07500)、中国气象局预报员专项(CMAYBY2018 005)及天津市气象局气象预报预警创新团队共同资助
引用文本:
尉英华,陈宏,何群英,林晓萌,张辉,2019.渤海西岸偏东风对天津局地大暴雨的影响分析[J].气象,45(1):61-72.
WEI Yinghua,CHEN Hong,HE Qunying,LIN Xiaomeng,ZHANG Hui,2019.Influence of Easterly Winds from West Coast of Bohai Sea on Local Heavy Rainfall in Tianjin[J].Meteor Mon,45(1):61-72.