俞小鼎,周小刚,王秀明. 2016. 中国冷季高架对流个例初步分析[J]. 气象学报, 74(6):902-918, doi:10.11676/qxxb2016.075
中国冷季高架对流个例初步分析
A preliminary case study of elevated convection in China
投稿时间:2016-03-25  修订日期:2016-08-30
DOI:10.11676/qxxb2016.075
中文关键词:  高架对流  条件不稳定  条件对称不稳定  俘获重力波  倾斜对流
英文关键词:Elevated convection  Conditional instability  Conditional symmetric instability  Trapped gravity wave  Slantwise convection
基金项目:国家自然科学基金项目(41475042)、国家973项目(2013CB430103)、公益性行业(气象)科研专项基金(GYHY201406002)。
作者单位
俞小鼎 中国气象局气象干部培训学院, 北京, 100081 
周小刚 中国气象局气象干部培训学院, 北京, 100081 
王秀明 中国气象局气象干部培训学院, 北京, 100081 
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中文摘要:
      通过对3个中国冷季高架对流个例进行详细分析,试图揭示中国冷季不同类型高架对流在环境背景、雷达回波结构、产生的天气类型和主要形成机理方面的主要特征,包括共同点和差异。利用常规高空和地面观测、NCEP分析和雷达回波资料,采用对不同类型多个典型个例分析的方法进行研究。首先给出了中国冷季高架对流的定义,然后分别仔细分析了3个不同类型冷季高架对流个例,探讨他们各自的环境背景特征,生成与发展机理,对他们的相同点和差异进行了对比。3个个例的共同特点是斜压性和深层风垂直切变都很强,对流发生区在地面锋面冷区一侧数百千米。不同点是前2个个例为条件不稳定结合水汽和抬升触发等条件导致的垂直对流,低层暖平流都很强,但对流有效位能差异很大,对流强度和导致的天气差异很大。第3个个例为条件对称不稳定结合水汽等条件形成的倾斜对流个例,倾斜对流区在地面锋面以北500-600 km处,冷垫非常深厚。第1个例子于2012年2月27日发生在华南,最不稳定气块对流有效位能只有100 J/kg左右,深层风垂直切变很强,850-700 hPa的辐合切变线触发了该高架对流,对流较弱,最强反射率因子在40-45 dBz,只产生了雷电、霰和小冰雹。第2个例子于2007年3月30日晚上出现在山东半岛,最不稳定气块对流有效位能达1400 J/kg,0-6 km风垂直切变(风矢量差)达32 m/s,形成数个结构类似超级单体的对流风暴,多个多单体强风暴,和大量多单体风暴,最强反射率因子将近70 dBz,导致6个站出现冰雹,其中1个站观测到直径23 mm的大冰雹,另1个站点出现21 m/s对流大风。其最有可能的触发机制是以泰山为中心的山地激发出来,在低层为稳定层,以上为深层条件不稳定层和强风垂直切变环境下形成的较大振幅俘获中尺度重力波。该俘获重力波可能还对对流生成后对流的组织形态和对流群的整体结构具有显著调制作用。最后1个例子是发生在2008年1月中国南方大范围冰冻雨雪期间1月27日安徽、江苏和浙江的区域性大暴雪,分析表明,条件对称不稳定导致的倾斜对流是产生此次大暴雪的主要原因之一。
英文摘要:
      The criteria for elevated convection in China are proposed first based on comprehensive reviews of international and domestic publications related to elevated convection. Three elevated convection cases are then analyzed using regular upper-air and surface observations, Doppler weather radar data and the NCEP reanalysis data. Major characteristics of the environmental background, radar echo structure, and genesis mechanisms for different types of elevated convection and their common features and differences are revealed. The common features of the three cases include strong baroclinicity and large vertical wind shears, and the convection area was located on the cold side several hundred kilometers away from the surface front in all the three cases. Differences among them are that, the vertical convection in the first and second cases was triggered by conditional instability coordinated with abundant water vapor and lifting, while convection in the third case was related to the slantwise convection caused by conditional symmetric instability that acted in concert with water vapor and lifting. The first case occurred in southern China on 27 February 2012 with a weak MUCAPE (100 J/kg) and a strong vertical wind shear within 0-6 km. Convection in this case was weak with the maximum reflectivity of around 40-45 dBz. This case produced lightning and graupels. The second case occurred in Shandong Peninsula on 30 March 2007 with a much higher MUCAPE (1400 J/kg) compared to that of the first case and a very strong vertical wind shear (wind vector difference between 0-6 km is 32 m/s) within 0-6 km. This case generated 2-3 supercell-like storms, several strong multi-cell cluster storms, and many weak multi-cell cluster storms. The maximum reflectivity of this case was about 65-70 dBz, and hails were observed at six weather stations with the maximum hail diameter of 23 mm, while wind gust up to 21 m/s was observed at one weather station. The most possible triggering mechanism for the strong elevated convection on 30 March 2007 is the trapped large-amplitude mesoscale gravity wave excited by the upstream Taishan mountains under favorable environmental conditions, i.e. a deep layer of conditional instability and strong vertical wind shears above a thick layer of low-level frontal inversion (cold stable boundary layer). This trapped large-amplitude mesoscale gravity wave also played an important role in modulating the organization pattern of the convective storms after their genesis. The third and last case is a severe snowstorm occurred on 27 January 2008 in Anhui, Jiangsu and Zhejiang provinces. The analysis shows that one of the major mechanisms for this severe snowstorm is the slantwise convection triggered by conditional symmetric instability. Several key issues are briefly discussed as well.
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