杨忠林,赵坤,徐坤,李凯,陈刚,温龙,刘溯,杨正玮. 2019. 江淮梅雨期极端对流微物理特征的双偏振雷达观测研究[J]. 气象学报, 77(1):58-72, doi:10.11676/qxxb2018.040
江淮梅雨期极端对流微物理特征的双偏振雷达观测研究
Microphysical characteristics of extreme convective precipitation over the Yangtze-Huaihe river basin during the Meiyu season based on polarimetric radar data
投稿时间:2017-12-25  修订日期:2018-05-07
DOI:10.11676/qxxb2018.040
中文关键词:  梅雨  极端对流  微物理特征  双偏振雷达
英文关键词:Meiyu  Extreme convection  Microphysical characteristics  Polarimetric radar
基金项目:国家重点基础研究发展计划(973)项目(2013CB430101)、国家重点研发计划项目(2017YFC1501703)、国家自然科学基金项目(41322032、41275031)。
作者单位E-mail
杨忠林 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093
中船重工鹏力(南京)大气海洋信息系统有限公司, 南京, 211106 
 
赵坤 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093 zhaokun@nju.edu.cn 
徐坤 中船重工鹏力(南京)大气海洋信息系统有限公司, 南京, 211106  
李凯 中船重工鹏力(南京)大气海洋信息系统有限公司, 南京, 211106  
陈刚 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093  
温龙 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093
西昌卫星发射中心, 西昌, 615000 
 
刘溯 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093  
杨正玮 中尺度灾害性天气教育部重点实验室, 南京大学大气科学学院, 南京, 210093  
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中文摘要:
      为研究梅雨期极端对流系统的微物理特征,利用2013—2014年江淮梅雨期间南京溧水S波段双偏振雷达探测资料和地面自动站小时降水资料,统计分析了两类极端对流降水系统的微物理特征及差异。这两类极端对流系统的定义基于地面降水强度和雷达回波顶高,分别为所有对流中降水强度最强的1%(R类:小时降水强度>46.2 mm/h)和对流发展高度最高的1%(H类:20 dBz回波顶高>14.5 km)。结果显示这两类极端对流系统仅有30%的样本重合,显示了二者之间的弱相关性。对于相同的反射率因子ZH,R类极端对流系统的近地面差分反射率因子ZDR通常较H类极端对流小约0.2 dB,表明R类极端对流具有较小的平均粒径。结合双偏振雷达反演的粒子大小和相态分布显示,虽然两类极端对流都表现出海洋性对流降水特征,但R类极端对流较H类极端对流的总体雨滴粒径更小而数浓度更高,导致R类极端对流系统的地面降水更强。与R类极端对流系统相比,H类极端对流系统的上升运动更强,将更多的水汽和过冷水输送到0℃层以上,有利于形成更大的冰相粒子(如霰粒子等),并通过融化形成大雨滴。以上研究表明,梅雨期降水强度和对流发展深度并没有必然的联系,极端降水主要是中等高度的对流引起。
英文摘要:
      The S-band polarimetric radar data and hourly rain gauge data during the Meiyu seasons of 2013 and 2014 were used to examine the microphysical characteristics of extreme convective precipitation over the Yangtze-Huaihe river basin. Two types of extreme convective precipitation features (PFs) are identified based on the top 1% rainfall rate (top-R) and the top 1% 20 dBz echo top height (top-H). Result shows that only ~30% of the samples are overlapped between these two types of PFs, which indicates a weak linkage between them. Microphysical differences between the top-R (characterized by R>46.2 mm/h in this study) and the top-H (H>14.5 km) are further analyzed. For the same ZH near the ground, ZDR values in top-R are always ~0.2 dB lower than that in top-H, indicating the former contains relatively smaller size. Combination of the drop size distribution (DSD) retrieval and hydrometeor classification results shows that both types of precipitation systems possess characteristics of maritime convection. However, top-R (top-H) PFs contain smaller (larger) raindrops with higher (lower) number concentration of raindrops, resulting in more (less) intense rainfall. On the other hand, the reflectivity of top-H PFs reaches higher altitude with stronger vertical velocity, resulting in more water vapor and super-cooled liquid water being transported aloft. Ice particles can grow larger (e.g., graupel and hail) and then melt into larger raindrops. This study shows that there is a weak correlation between the rainfall intensity and the depth of convection while the extreme rainfall is usually accompanied by moderate convection during the Meiyu season.
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