一次强降水超级单体的双偏振雷达观测分析

Analysis of a high precipitation supercell based on dual polarization radar observations

中文关键词:  双偏振雷达  强降水超级单体  风场反演  粒子相态识别

英文关键词:Dual polarization radar  High precipitation supercell  Wind retrieval  Hydrometeor classification

中文摘要:

      为分析强降水超级单体风暴的偏振特征及其动力和云物理结构，利用厦门海沧双偏振雷达数据及常规观测资料，采用多普勒雷达风场反演和粒子相态识别等技术，对2018年5月7日发生在闽南地区的一次导致特大暴雨的强降水超级单体风暴进行了分析，研究表明：（1）相关系数小值区出现在有界弱回波区和钩状回波之前，可指示低层上升气流的位置。（2）在前侧下沉气流南侧的反射率因子梯度大值区附近，存在一个浅薄的差分反射率因子大值区（差分反射率因子弧），其形态与超级单体的发展程度有关。在本次过程中差分反射率因子弧先于钩状回波和中气旋出现，对超级单体的发展具有较好的指示性。（3）在中层的融化层上，差分反射率因子大值区和相关系数小值区呈环形围绕在上升气流周围。差分反射率因子环和相关系数环对确定中层上升气流的位置具有指示意义。（4）差分反射率因子柱位于有界弱回波区的上方，并位于主上升气流附近，在仅有单部雷达进行观测时，差分反射率因子柱可用于识别主上升气流的位置。（5）差分相位常数柱主要由大量混合相态水凝物造成，其位置与地面雨强中心存在较好的对应关系。

英文摘要:

      A high precipitation (HP) supercell accompanied with extremely heavy rainfall in southern Fujian on 7 May 2018 is analyzed based on observations of dual polarization radar and conventional observations. The polarimetric signatures and dynamic and microphysical characteristics of the HP supercell are analyzed using the Doppler radar wind field retrieval and hydrometeor classification technique. The study yields the following results. (1) In the absence of a clearly defined bounded weak-echo region (BWER) and the hook echo, the area of decreased cross-correlation coefficient (CC) can be used as a proxy for the updraft location. (2) A shallow region of very high differential reflectivity (Z_dr) is found along the peak reflectivity gradient on the southern edge of the forward flank downdraft (FFD), which is termed as Z_dr arc. The Z_dr arc morphology is associated with the development of the HP supercell. During this process, the occurrence of Z_dr arc was earlier than that of the hook echo and the mesocyclone, which is a favorable index of the development of the supercell storm. (3) A mid-level circular ring of enhanced Z_dr and depressed CC were found above the environmental melting layer, surrounding the updraft. The Z_dr ring and CC ring are good indicators of the updraft location at the mid-level. (4) The Z_dr column was above the BWER, which was located at the vicinity of the main updraft. Z_dr column can be used to identify the main updraft location, particularly when only a single dual-polarization radar data is available. (5) The K_dp column was primarily composed of a large number of mixed-phase hydrometeors, whose location was related with the rainfall intensity center in the surface.