青藏高原东南部墨脱地区弱降水微物理特征的Ka波段云雷达观测研究  

Study of the Microphysical Characteristics of Weak Precipitation in Mêdog,Southeastern Tibetan Plateau Using Ka-Band Cloud Radar

作　　者：张静怡 王改利[2] 郑佳锋[1] 刘黎平[2] 周任然 ZHANG Jingyi;WANG Gaili;ZHENG Jiafeng;LIU Liping;ZHOU Renran(Schools of Atmospheric,Chengdu University of Information Technology,Chengdu 610225;State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Science,Beijing 100081)

机构地区：[1]成都信息工程大学大气科学学院,成都610225 [2]中国气象科学研究院灾害天气国家重点实验室,北京100081

出　　处：《大气科学》2022年第5期1239-1252,共14页Chinese Journal of Atmospheric Sciences

基　　金：第二次青藏高原综合科学考察研究2019QZKK0105;国家重点研发计划项目2018YFC1505702;国家自然基金项目项目41775036。

摘　　要：藏东南地区的墨脱县位于雅鲁藏布江下游的河谷区域,是印度洋水汽进入高原的最主要水汽通道。墨脱作为西藏年平均降水量最多的地区,是青藏高原云降水系统的重要组成部分。本文以2020年墨脱地区的Ka波段云雷达观测数据为基础,首先对云雷达功率谱数据进行预处理,并采用降水现象仪对云雷达观测进行验证。在此基础上,选取了2020年3月6日和8月24日具有层状云降水特性的两次弱降水过程,利用云雷达功率谱数据反演了雨滴谱,探究墨脱地区旱季和雨季弱降水的微物理特征。结果表明:云雷达观测与降水现象仪雨滴谱数据计算的Ka波段云雷达回波强度理论值存在大约12 dB的系统误差,订正之后二者随时间变化一致性较好,云雷达反演的近地面雨滴谱特征与降水现象仪观测接近。墨脱地区零度层高度随季节变化明显,旱季零度层高度较低(例如地面上1.5 km左右),而雨季零度层高度较高(例如地面上4 km左右)。墨脱层状云雨滴谱的宽度较窄,降水粒子直径不超过3 mm。在零度层以上,根据谱偏度和峰度的垂直变化可以推测冰晶粒子直径随高度下降缓慢增长,但旱季冰晶粒子增长比雨季更为明显。经过零度层后,冰晶粒子转化为雨滴,雨滴在下落过程中由于碰并及蒸发作用造成浓度减小,直径越小的粒子浓度减小越快。在近地面,由于蒸发作用的加强导致随高度降低雨滴浓度明显减小。Mêdog,located in the southeastern Tibetan Plateau(TP)and the valley of the lower reaches of the Yarlung Zangbo River,is the main water vapor channel from the Indian Ocean to the TP.Mêdog is also an important part of the TP precipitation system because it has the largest annual average precipitation amount over the TP.Based on the Ka-band cloud radar(KaCR)observation data of the Mêdog National Climate Observatory in 2020,this study first preprocessed the power spectrum data of the KaCR,which were verified by comparing with measurements from a collocated precipitation phenomenometer.Then,two weak stratiform precipitation processes that occurred on March 6 and August 24,2020,were selected,and the raindrop size distribution(RSD)was retrieved from the power spectrum data of the KaCR to explore the microphysical characteristics of weak precipitation in the dry and rainy seasons in Mêdog.Results showed that the systematic error of the reflectivity factor reached approximately 12 dB between KaCR measurements and theoretical values of KaCR calculated from the observations using the precipitation phenomenometer.Good consistency between the two datasets is evident after KaCR was corrected.Furthermore,the near-surface RSDs retrieved from KaCR was close to those observed from the precipitation phenomenometer.The heights of the bright band in Mêdog varied with the seasons and were low in the dry season(i.e.,approximately 1.5 km above ground level)and high in the rainy season(i.e.,approximately 4 km above ground level).The spectral width of the RSD of the weak stratiform precipitation cases was narrow,and the diameter of the raindrop did not exceed 3 mm in Mêdog.Above the bright band,the diameter of small ice particles gradually increased with the decrease in height according to the spectrum skewness and kurtosis.However,the growth of ice particles in the dry season is more obvious than that in the rainy season.Below the bright band,the ice particles converted into liquid water drops,whose concentration decreased as the h

关 键 词：青藏高原 毫米波雷达 功率谱 垂直结构 微物理过程 

分 类 号：P412[天文地球—大气科学及气象学]