赵坤. 2018. 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, (0):-, 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 Yangtze-Huaihe River Basin during Meiyu Season using Polarimetric
投稿时间:2017-12-12  修订日期:2018-03-21
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;国家自然科学基金
作者单位E-mail
赵坤 南京大学大气科学学院 zhaokun@nju.edu.cn 
摘要点击次数: 470
全文下载次数: 457
中文摘要:
      为研究梅雨期极端对流的微物理特征,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类极端对流的地面降水更强。同R类极端对流相比,H类极端对流的上升运动更强,将更多的水汽和过冷水输送到0 °C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:
      In this study, the S-band polarimetric radar data and hourly rainfall data from rain gauges during Meiyu season of 2013 and 2014, are selected to examine the microphysical characteristics of extreme convective precipitation over Yangtze-Huaihe river basin. Two types of extreme convective precipitation features (PFs) are identified based on the top 1% rainfall rate (top-R convective PFs) and the top 1% 20 dBZ echo top height (top-H convective PFs). Result shows that only ~30% of the samples are overlapped between these two types of PFs, which indicate a weak linkage between them. Microphysical differences between the top-R convective PFs (characterized with R> 46.2 mm h-1 in this study) and the top-H convective PFs (H>14.5 km) are further analyzed. ZDR values in top-R convective PFs are always ~0.2 dB lower than that in top-H convective PFs near the ground, indicating the former contains relatively smaller size. The drop size distribution (DSD) retrieval and hydrometeor classification results show that despite the two types of extreme convective PFs are all characterized as maritime convection, but top-R convective PFs contains relatively smaller size but higher number concentration of raindrops, resulting in more intense rainfall. Compared with top-R convective PFs, the reflectivity of top-H convective PFs reached higher altitude with stronger vertical velocity, thus more water vapor and super-cooled liquid water are transported aloft, ice particles then grown larger through cold cloud processes. Larger ice-phase particles (i.e. graupel and hail) usually melted to larger raindrops (which have higher efficiency of collecting small raindrops and cloud droplets) after descending across the melting layer, and ultimately producing larger raindrops. The above study shows that there is a weak linkage between the rainfall intensity and the depth of convection and the extreme rainfall is usually caused by moderate convection during Meiyu Season.
查看全文   查看/发表评论  下载PDF阅读器
分享按钮