利用多普勒雷达径向速度提取台风环境风场信息

Extracting Typhoon Environmental Wind Field Using Doppler Radar Radial Velocity

应用蓝金模式模拟了纯气旋性旋转的多普勒雷达径向速度特征,还模拟了不同环境风向和吹向台风中心的辐合风对台风多普勒速度特征的影响。在此基础上,提出了雷达实测台风速度的特征和不同环境风向的速度数值模拟图进行比较,从而提取出相应环境风信息的方法,并应用这种环境风信息来判断台风的移动路径。通过对台风实例分析,特别是在台风发生转折的关键时刻,该方法都能够较准确地判断环境风转折的多普勒速度特征。应用多普勒雷达径向速度图像与不同环境风向模拟图像进行比较的方法,能够实时(雷达观测时间间隔仅为6 min)监测到环境气流的方向及其变化,比较准确地监测台风的移动路径,这是其他大尺度气象资料难以做到的。分析表明:环境风转向变化的现象在前,台风发生转折的现象在后,对台风路径的短时预报具有一定应用价值。

It is always a challeging subject to forecast landing path of tropical cyclone and related wind distribution in operational weather forecast.Therefore,Doppler radar radial velocity is applied to the short-term weather forecast as a new attempt.Rankine model is used to simulate the characteristics of the Doppler velocity （CDV） in the pure cyclone,and the impacts of both different environmental wind directions and convergent wind towards typhoon center are considered.Based on the simulation,the method of extracting typhoon environmental wind information is brought up,and then the extracted environmental wind is applied to judge the typhoon path.Comparison of radar observation and numerical simulation typhoon wind mainly focuses on three aspects：Deviation of typhoon center from zero velocity line,curvature difference of zero velocity line and difference between orders of positive and negative extreme velocities.A number of typhoon cases have been analyzed,especially during the key time of the turning of typhoon path,and it indicates that this method is good enough to judge the turning of the environmental wind of the CDV.At the same time,by comparing the Doppler radar velocity image and the simulation of different environmental wind directions,the direction and its change of the environmental air flow can be real-time monitored（only 6 minutes for the interval of radar observation）,so that the typhoon path can be well monitored,while this can hardly be achieved with large-scale meteorological data.In particular,the turning of environmental wind occurs before the turning of typhoon path.For instance,the movement path of typhoon Aere changes from westward to southwestward and the simulation shows that there is an obvious change of the environmental wind more than 3 hours ago.For typhoon Nock-Ten,when its movement path changes from northward to northwestward,the environmental wind direction changes from southward to southward by eastward at least 1 hour in advance.These results are important for the short-term forecast of typhoon path both theoretically and practically.The stronger a typhoon is,the more obvious cyclonical circulation is, and thus the method performs better in estimating typhoon path,otherwise typhoon environmental wind information may affect the accuracy.