双偏振雷达资料同化对一次台风降雨模拟的影响

Effect of the Dual-Polarization Radar Data Assimilation on Rainfall Simulation of Typhoon Hato

作者：

王德立深圳市气象局；深圳南方强天气研究重点实验室深圳 518040
孔凡铀俄克拉荷马大学风暴分析和预报中心诺曼（美国） 73072
王洪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 510640
陈训来深圳市气象局；深圳南方强天气研究重点实验室深圳 518040

中文摘要：

双偏振雷达同时或交替进行水平偏振和垂直偏振方向的观测，其观测量可以更加准确描述降水云微物理特征。这些云微物理特征与强对流系统发生发展密切相关。因此利用雷达偏振量观测来改进强对流天气数值预报具有非常重要的现实意义。在利用包含非标准遮挡去除、水凝物分类筛选、偏振量阈值检查、杂波剔除和平滑等步骤的质量控制模块实现双偏振雷达资料质量控制基础上，使用改进的ARPS云分析模块实现双偏振雷达资料的同化。改进的ARPS云分析模块主要通过基于T-matrix方法的雷达算子以及水凝物分类算法实现偏振量的同化。首先利用水平反射率因子（Zh）、差分反射率（ZDR）、差传播相移率（KDP）、零滞后互相关系数（ρHV）和模式背景场气温进行水凝物模糊逻辑分类从而确定三种主要水凝物类型（雨、雪、雹/霰）各自占比，然后根据基于T-maxtrix方法的雷达算子分析出这三种水凝物的混合比。利用广州、清远、韶关和阳江等四部S波段双偏振雷达资料对2018年台风天鸽个例进行同化分析模拟试验。结果表明，偏振量同化使得该台风初始分析场的水凝物分布更加合理，水汽混合比减小，700 hPa台风周围出现干舌；偏振量同化对这次台风强降雨短时预报有一定正影响。

中文关键词：

双偏振雷达，资料同化，云分析，台风

KeyWords：

dual-polarization radar, data assimilation, cloud analysis, typhoon

Abstract：

The polarimetric variables from dual-polarization radar can more accurately describe the microphysical states in a convective storm. These microphysical states are closely related to the occurrence and development of severe convection systems. Therefore, it is great practical significance to improve the numerical forecast of severe convection weather by using radar dualpolarization measurements. Based on the quality control of polarimetric radar measurements (including non-standard blockage removal, hydrometeor classification, polarization threshold test, and clutter removal and smoothing), the S-band dual-polarization radar data are assimilated by the improved ARPS cloud analysis system .The improved ARPS cloud analysis system makes the polarization assimilation mainly by the hydrometeor classification algorithm and the radar operator based on T-matrix method, based on the principles of fuzzy logic, polarimetric radar measurements (including horizontal reflectivity (Zh), differential reflectivity (ZDR), specific differential phase (KDP), correlation coefficient (ρHV) and background temperature) are used to classify hydrometeors and determine the ratios among the three main hydrometeor types (rain, snow, hail/graupel). And then the mixing ratio of each type is analyzed using the reflectivity operator which based on T-maxtrix method to comply with the Zh observation. The S-band dual-polarization radar data of Guangzhou, Qingyuan, Shaoguan and Yangjiang are assimilated in Typhoon Hato (No. 1713). The results show that the initial hydrometeors distribution is improved when the polarimetric variables are assimilated. The water-vapor mixing ratio is decreased, and a dry tongue appears around the typhoon at 700 hPa. Moreover, there are less false alarms for heavy rainfall. Significant positive impacts on the short-term forecast of heavy rainfall are obtained in the typhoon case.