doi:  10.3878/j.issn.1006-9895.1812.18206
湖北三类组织形态强对流系统造成的地面强对流大风特征

Characteristics of Strong Convective Wind Events Caused by Three Types of Convective Systems in Hubei Province
摘要点击 327  全文点击 215  投稿时间:2018-07-30  
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基金:  公益性行业(气象)科研项目GYHY201506006公益性行业(气象)科研项目(GYHY201506006)
中文关键词:  强对流大风  组织形态  入流大风  地形  后向传播
英文关键词:  Strong convective wind  Organization form  Inflow gale  Terrain  Backward-propagation
     
作者中文名作者英文名单位
郭英莲中国气象科学研究院灾害天气国家重点实验室,北京100081;中国气象局武汉暴雨研究所,武汉430205
孙继松中国气象科学研究院灾害天气国家重点实验室,北京100081
引用:郭英莲,孙继松.2019.湖北三类组织形态强对流系统造成的地面强对流大风特征[J].大气科学,43(3):483-497,doi:10.3878/j.issn.1006-9895.1812.18206.
Citation:.2019.Characteristics of Strong Convective Wind Events Caused by Three Types of Convective Systems in Hubei Province[J].Chinese Journal of Atmospheric Sciences (in Chinese),43(3):483-497,doi:10.3878/j.issn.1006-9895.1812.18206.
中文摘要:
      利用湖北省2012~2017年区域自动站、天气雷达和周边探空站观测资料,对三类不同组织形态的中尺度对流系统(Mesoscale Convective System, MCS)(线性MCS、非线性MCS和孤立对流风暴)造成的地面强风(极大风速≥17 m/s)的时空分布、移动与传播、对流环境特征等方面进行了统计对比分析,并结合个例讨论了地面入流大风的成因及其对对流系统发展、组织的影响。结果表明:(1)大量的非线性MCS可能是由更早发生在山区和丘陵的孤立对流风暴向平原地区移动过程中组织形成的,孤立对流风暴造成的地面大风出现的峰值时间在17:00(北京时,下同)前后,非线性MCS地面大风的峰值时间在19:00左右;线性MCS造成的强对流大风主要出现在平原地区。(2)非线性MCS和孤立对流风暴是造成湖北省地面大风的主导系统,其中,非线性MCS造成的地面大风站次数占强对流大风站次总数的41.9%,而39.3%的地面强对流大风站次是由孤立对流风暴造成的。(3)虽然大于17 m/s的地面入流大风占所有强对流大风的比例很小,但存在地面入流大风的强对流系统的影响范围、持续时间均远大于同一类型对流系统的平均值。基于一次长生命史线性MCS(飑线)造成强对流大风事件的分析表明:雷暴系统前侧的地面入流大风是由对流强烈发展造成,这支暖湿入流又进一步增强了对流风暴的发展,同时地面入流大风的形成进一步加强了垂直风切变,因而强的地面入流更有利于对流系统的组织化发展。(4)虽然暖季强对流系统的平均引导气流均以西南风为主,但线性MCS主要自西向东移动、非线性MCS以自西南向东北移动为主、孤立对流风暴的移动方向则更具多样性,也更易出现后向传播现象。孤立对流风暴相对组织化的强对流系统而言,往往发生在更不稳定或更干的层结大气中,且环境垂直风切变更弱、风速更小。
Abstract:
      Using regional automatic weather station (AWS) data, together with radar and sounding over Hubei Province from 2012-2017, in this study, the authors classified the mesoscale convective systems (MCSs) that result in surface convective gales in Hubei (maximum wind speed ≥ 17 m/s) into three types (linear MCSs, nonlinear MCSs, and isolated convective storms). The temporal and spatial distributions of convective gales, the movement and propagation of corresponding convective systems, and their convective environments were investigated. The mechanism of the convective inflow gale and the roles of convection system organization and development are discussed, with particular reference to one case. The results indicate that: (1) A large number of nonlinear MCSs may be formed by isolated convective storms occurring in mountains or hills, which then move toward the plains. The peak time of the surface gales caused by isolated convective storms during the study period was around 1700 BJT (Beijing time), and the highest surface-gale frequency corresponding with nonlinear MCSs appeared around 1900 BJT. Gales caused by linear MCSs mainly occurred in plain areas. (2) Nonlinear MCSs and isolated convective storms were the primary systems triggering gales in Hubei, with 41.9% of the gales at the stations caused by nonlinear MCSs and 39.3% by isolated convective storms. (3) Although inflow gales on the surface account for only a small proportion, their corresponding convective systems were much larger and their durations much longer than the average of the same type. A case study of a long-life linear MCS (squall line) shows that the ground inflow gales were caused by the strong development of convection, and the moist warm inflow in front of the convective system enhanced the convective activity developing as feedback. Meanwhile, the inflow gales strengthened the vertical wind shear in the forward direction. This is why the strong ground inflow was more conducive to the organizational development of the convective system. (4) Although southwesterly winds constituted the mean steering flow in all three system types, linear MCSs mainly moved from west to east, nonlinear MCSs moved mostly from southwest to northeast, and isolated convective storms moved in more diverse directions with more backward-propagation phenomena. Relative to organized convective systems, isolated convective storms often occurred in more unstable or drier environments with weak vertical wind shear and lower wind speeds.
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