梅垚,胡志群,黄兴友,陈超. 2018. 青藏高原对流云的偏振雷达观测研究[J]. 气象学报, 76(6):1014-1028, doi:10.11676/qxxb2018.037
青藏高原对流云的偏振雷达观测研究
A study of convective clouds in the Tibetan Plateau based on dual polarimetric radar observations
投稿时间:2017-11-24  修订日期:2018-05-03
DOI:10.11676/qxxb2018.037
中文关键词:  青藏高原地区  对流云  双偏振雷达  风场反演  相态识别
英文关键词:Tibet Plateau  Convective cloud  Dual-polarization radar  Wind field retrieval  Class classification
基金项目:第三次青藏高原大气科学试验——边界层与对流层观测(GYHY201406001)、国家自然科学基金项目(41375038)。
作者单位E-mail
梅垚 南京信息工程大学气象灾害预报预警与评估协同创新中心, 南京, 210044
中国气象科学研究院灾害天气国家重点实验室, 北京, 100081 
 
胡志群 中国气象科学研究院灾害天气国家重点实验室, 北京, 100081 huzq@cma.gov.cn 
黄兴友 南京信息工程大学气象灾害预报预警与评估协同创新中心, 南京, 210044  
陈超 广东省气象台, 广州, 510640  
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中文摘要:
      利用可移动式C波段双偏振雷达(C-POL),以及那曲新一代天气雷达(CINRAD/CD)于2014年7月30日和8月5日在西藏那曲地区的观测资料,并通过双多普勒雷达风场反演、偏振雷达相态识别,清晰展示了这两次高原冰雹云发生发展的动力、微物理、热力结构特征。结果表明:青藏高原地区的对流云多在午后出现,水平及垂直尺度不大,但是对流云发生频繁、生消快,一般持续几十分钟。从RHI扫描的水平偏振反射率因子(ZH)、差分反射率因子(ZDR),以及反演的相态(Class)分布上可以明显看出,粒子跟随"0线"抬高,不断增长,回波强度也越来越大,并最终超过主上升气流从另一侧降落,形成冰雹墙的整个动力与微物理过程。从连续时次的RHI上还观测到一次对流单体发生、发展过程中相态从湿雪到冰雹的变化,单体刚刚触发时,回波高度不高,强度还很弱,但是却出现成片的湿雪区域,说明上升气流非常旺盛,将本来落到0℃层以下的未完全融化的湿雪重新带到0℃层以上,通过凝华、凇附、攀附等物理过程,仅仅10多分钟,这些湿雪就能够迅速增长成为冰雹。这些湿雪重新凝结过程中,释放潜热,进一步促进了不稳定结构,加强了上升气流和下沉气流。因此,如果某个刚刚生成的弱回波区域内,在融化层以上出现大量的湿雪,往往预示着该区域上升气流强劲,会迅速发展成强回波单体。
英文摘要:
      Based on observations of a mobile C-band dual polarimetric radar (C-POL) and the Chinese new generation weather radar deployed in Naqu (CINRAD/CD) from 30 July to 5 August 2014, two hailstorm events and their associated dynamic, thermal-dynamic and microphysical characteristics are demonstrated using wind fields retrieved from observations of the two Doppler radars and identification technique of dual polarization radar hydrometeors. The convective cells mostly appeared in the afternoon in the Tibetan Plateau. Although the horizontal and vertical scales of the convective cells are small, they occurred frequently and evolved rapidly, and generally lasted for tens of minutes. In the RHI (range height indicator) images of ZH, ZDR and Class, the dynamic and microphysical processes can be seen clearly. Hydrometeor particles reached higher levels following the "0 line" and grew quickly, accompanied by increases in the echo intensity, and eventually formed a hail wall dropping down on the other side of main updraft. From the consecutive three RHI scans, it can be seen that the particles changed from wet snow to hailstorm during the evolutional process in one convective cell. The height of the echo was lower and its intensity was very weak when the convective cell was initially triggered. However, large amounts of wet snow appeared above the melting level, indicating that the updraft was strong enough to transport wet snow back to higher levels before the snow completely melted below the melting level. Through physical processes such as condensation, rime and attachment, the wet snow could rapidly grow into hailstones in just over 10 min. During the re-condensation of wet snow, the unstable structure further developed while the ascending and descending motions strengthened due to the latent heat release. Therefore, the occurrence of wet snow in a newly generated weak echo region above the melting level usually indicates strong updraft and convective cell would develop rapidly.
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