| 一次华南超级单体风暴的S波段偏振雷达观测分析 |
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| 引用本文： | 王洪,吴乃庚,万齐林,詹棠.一次华南超级单体风暴的S波段偏振雷达观测分析[J].气象学报,2018,76(1):92-103. |
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| 作者姓名： | 王洪 吴乃庚 万齐林 詹棠 |
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| 作者单位： | 1.中国气象局广州热带海洋气象研究所/中国气象局广东省区域数值天气预报重点实验室, 广州, 510080 |
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| 基金项目： | 国家自然科学基金（41475102、41461164006、41705035）、公益性行业（气象）科研专项（GYHY201406003）、广东省科技计划项目（2017A020219005）、广东省自然科学基金项目（2016A030313140）和广东省公益研究与能力建设计划项目（2017B020218003）。 |
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| 摘 要： | 利用珠海与澳门共建的中国首部S波段业务双偏振雷达探测资料、风廓线资料和地面加密观测资料,对2015年4月20日发生在珠海附近的一次典型华南春季冷锋触发的超级单体风暴的偏振观测特征进行了分析。天气分析表明,风暴发生于地面冷锋和低空切变线附近,中等对流不稳定（对流有效位能为1300 J/kg）和较强风垂直切变（0-6 km风矢量差为20 m/s）环境中。环境总理查逊数为18,与中纬度典型超级单体的生成环境接近,风暴相对螺旋度为2.9 s-1。偏振观测分析表明,大雹粒子的翻滚使冰雹区具有水平反射率因子高（>50 dBz）、差分反射率低（-1-0.5 dB）的特点;雨和冰相粒子的混合导致了相关系数的下降（小于0.9）;比差分相位观测对冰雹并不敏感（比差分相位与水平反射率因子的线性拟合率仅为0.05）。在混合相粒子和液相粒子的共同作用下,融化层附近存在差分反射率增大、相关系数减小的现象。风暴侧前方下沉气流偏东侧边界（水平反射率因子梯度高值区）存在一条“差分反射率弧”（差分反射率高值区）,主要由大雨滴构成,粒子分选机制合理解释了其形成原因。同时,相对较大的环境风使差分反射率弧更加远离（相对北美观测事实）风暴主体。风暴水平反射率因子中心附近存在“差分反射率柱”,与大雨滴被上升气流（连续分布的正径向风）带入高层冻结且失去取向稳定而导致差分反射率值迅速减小有关。
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| 关 键 词： | 双偏振雷达 超级单体 冰雹 差分反射率特征 |
| 收稿时间： | 2017/1/10 0:00:00 |
| 修稿时间： | 2017/8/4 0:00:00 |
Analysis of S-band polarimetric radar observations of a hail-producing supercell |
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| WANG Hong,WU Naigeng,WAN Qilin and ZHAN Tang.Analysis of S-band polarimetric radar observations of a hail-producing supercell[J].Acta Meteorologica Sinica,2018,76(1):92-103. |
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| Authors: | WANG Hong WU Naigeng WAN Qilin and ZHAN Tang |
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| Institution: | 1.Guangzhou Institute of Tropical and Marine Meteorology/Key Laboratory of Regional Numerical Weather Prediction, CMA, Guangzhou 510080, China2.Zhuhai National Climate Observatory, Zhuhai 519000, China |
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| Abstract: | The Zhu-Macao polarimetric radar data are used to analyze the structure and microphysics of a supercell near Zhuhai during 07:00-10:00 UTC 20 April 2015 (hereafter "4.20" supercell case). The storm occurred near the surface cold front and the low-level shear line, where the CAPE was 1300 J/kg and the wind shear between 0 and 6 km was greater than 20 m/s. The total Richardson number was 18, which is close to the value for typical mid-latitude supercell and the relative helicity of the storm was 2.9 s-1. A number of distinctive polarimetric signatures are found in the storm. The most remarkable signatures of hails were low differential reflectivity (ZDR) (-1 to 0.5 dB) and high reflectivity at horizontal polarizations (ZH) (>50 dBz). Because of tumbling, the ZDR of large hail area was close to 0. The cross-correlation coefficient (CC) was lower than 0.9 in the rain-hail mixtures and the hails had a negligible influence on the specific differential phase (KDP) (the slope of linear regression between ZH and KDP was 0.05). Because of the mixed phase particles and the liquid particles, a characteristic of enhanced ZDR and depressed CC was found near the updraft-perturbed melting layer. A shallow region of high ZDR (>3 dB) was found in the east edge of the forward-flank downdraft (FFD), called the "ZDR arc", which was associated with large, oblate raindrops. The size-sorting mechanism can explain this phenomenon. Compared to observations in North America, the higher environmental winds made the ZDR further away from the ZH center in the "4.20" supercell case. The ZDR columns were observed near the ZH center. The reason is that large raindrops were brought to the upper layer by updrafts and then losed orientation stability when they froze, thereby the ZDR values decreased significantly. |
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| Keywords: | Dual polarimetric radar Supercell Hail ZDR characteristic |
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