雷达资料同化在可致龙卷的强暴雨系统分析中的一些应用
Applications of a Real Time Weather-Adaptive 3DVAR Analysis System in Detections and Warning of Tornado Related Severe Weather
中文摘要：
近十几年来，一直致力于开发一个适用于对流尺度的三维变分同化系统。在最近版本的系统中，目标函数定义为包括背景项、观测项（包括常规观测、雷达径向风和反射率）和一些弱约束项。背景误差协方差矩阵的空间相关是通过递归滤波的方法来实现的。并且利用了背景误差协方差矩阵的平方根使目标函数的条件数减小，从而加速了求解过程。在系统研发的初期阶段，把重点放在对雷达径向风的分析上，最近几年的研究延伸到了在变分框架内对反射率资料的同化上。在此基础上，为NOAA的“基于数值模式的预警”研究课题发展了一个根据当前天气形势的演变，动态定位分析区域的实时高频率（5min）、高分辨率（1km）风场分析系统。文中将给出几个实例分析。在NOAA灾害性天气试验基地的初步评估中，该实时系统得到了很好的评价。在结论部分将简要介绍两种新的资料同化方法：集合三维变分同化、混合三维变分和卡尔曼同化方法。当前正在评估这些方法在对流尺度强风暴天气分析和预报中的应用。
中文关键词：
三维变分分析，龙卷，超级单体，雷达资料同化
KeyWords：
3DVAR analysis, tornado, supercell, radar data assimilation
Abstract：
A three-dimensional variational data assimilation scheme (3DVAR) has been explored for convective scale NWP. In this scheme, a cost function is defied with a background term, an observation term, and a weak constraint term. The background error covariance matrix, though simple, is modeled by using a recursive filter. Furthermore, the square root of this matrix is used to precondition the minimization problem. In its earlier development, only radar radial velocity data could be assimilated. Recent developments include the capability to assimilate reflctivity directly in this 3DVAR framework. Based on this 3DVAR framework, a real-time, weather-adaptive analysis system has been developed for the NOAA Warn-on-Forecast (WoF) project to incorporate all available radar observations within a moveable analysis domain. The system has ability to automatically detect and analyze severe local hazardous weather events at 1 km horizontal resolution every 5 minutes in real time based on the current weather situation, and can identify strong circulations embedded in thunderstorms. The system performed very well within the NOAA Hazardous Weather Testbed Experimental Warning Program and received good evaluations from forecasters. Several real data cases are given in this paper. In the conclusion part, we shall briefl introduce two new methods ensemble 3DVAR, and hybrid 3DVAR and EnKF schemes and discuss their potential applications for convective scale NWP