An improved hydrometeor identification method for X-band dual-polarization radar and its application for one summer Hailstorm over Northern China
An improved hydrometeor identification method for X-band dual-polarization radar and its application for one summer Hailstorm over Northern China
复制标题
改进的X波段双偏振雷达水凝物识别方法及其在华北夏季冰雹天气中的应用
DOI：
10.1016/j.atmosres.2020.105075
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发表时间：
2020
影响因子：
5.5
通讯作者：
Xiaoling Zhang
中科院分区：
文献类型：
--
作者：
Chuanhong Zhao;Yijun Zhang;Dong Zheng;Yunjun Zhou;Hui Xiao;Xiaoling Zhang
目前，车载移动的X波段双极化雷达（X-pol）获得的高分辨率强风暴观测资料已广泛应用于强风暴结构和动力学研究，但基于X-pol的冰雹识别尚不多见，导致X-pol在强风暴微物理过程中水凝物识别的应用受到限制。本文在前人工作的基础上，构造了一种改进的X-pol雹云水凝物识别（HID）方法;水凝物类别包括指示冰雹正在融化或经历湿增长的雨-冰雹混合物（RH）类别，水平和垂直极化回波之间的相关系数（ρHV）在暴雨中，利用混合相区的概念来定位暴雨中的局部混合相区，以避免该局部混合相区的环境温度对水凝物的分类造成的错误。改进后的HID方法可以看到融化层上方的液态水信息，为观测融化层上方冰雹湿生长的微物理过程提供了可能。利用中国科学院大气物理研究所X-pol卫星对一次北方夏季冰雹天气过程的高时空分辨率资料进行了分析。结果表明：识别出的相对湿度与中国气象局国家气象台的地面降雹记录基本一致，比差相位（KDP）柱比差反射率（ZDR）柱对上升气流带移动的指示更敏感，认为降雹关键区与地面降雹中心的相对位置（KAH，其中ZDR柱以上，ZDR~ −2 ~ 0 dB，ZH~ ≥ 50 dBZ）和上升气流区（由ZDR，KDP柱表示）将决定冰雹的演变。此外，KAH上层的高密度谷粒（HDG）可能是RH胚胎的来源，这些HDG从位于KAH后面的液态水富集区（LWR）收集液滴，以在KAH下层形成大量RH。这些特征对冰雹的预报和预警具有重要意义。
Currently, high-resolution severe storm observations obtained by vehicle-mounted mobile X-band dual-polarization radar (X-pol) are widely used in severe storm structure and dynamics studies; however, the identification of hailstones based on X-pol is still rare, leading to the limited application of X-pol in identifying hydrometeors in the microphysical processes of severe storms. Based on previous works, this study constructs an improved X-pol hydrometeor identification (HID) method for hailstorms; the hydrometeor categories include a rain-hail mixtures (RH) category indicating hailstones are melting or experiencing wet growth, and the correlation coefficient between horizontally and vertically polarized echoes (ρHV) is used to locate the local mixed phase region in storms to avoid misclassifications of hydrometeors resulted by environmental temperature in this local mixed phase region. The improved HID method can see liquid water information above the melting layer; it provides a possibility to observe the microphysical process of hailstones wet growth above the melting layer. Furthermore, this improved HID method was utilized to study the high spatiotemporal resolution data collected by the Institute of Atmospheric Physics of Chinese Academy of Sciences (IAP) X-pol for one summer hailstorm over northern China. The results indicate that the identified RH is consistent with the surface hail record of National weather observatory of China Meteorological Administration (CMA), the specific differential phase (KDP) column is more sensitive than the differential reflectivity (ZDR) column for indicating the updraft zone movement, and we considered that the relative position between the key area of hail (KAH, where above theZDRcolumn,ZDR~ −2 to 0 dB,ZH~ ≥ 50 dBZ) and the updraft zone (indicated by theZDR,KDPcolumn) will determine the evolution of hail. Furthermore, high-density graupels (HDGs) in the upper layer of the KAH may be the source of RH embryos, and these HDGs collect liquid droplets from the liquid water-rich (LWR) area located behind the KAH to form a large number of RH in the lower layer of the KAH. These characteristics are important for hailstone forecasting and warnings.