台风“碧利斯”的雷达反演及改进

利用两步变分反演方法，研究2006年第4号台风“碧利斯”，对照单部雷达资料和两部雷达资料的反演结果。结果表明：利用单部雷达资料不能很好的反演出台风的风场结构特征，而两部雷达资料在第一步反演背景场时，可以看出台风的涡旋特征。通过检验发现，此次台风过程的水平切向风在最大风速半径内部与Rankine模型相近，外部与Chen 3模型接近。为了更有效地利用单部雷达的观测信息准确定位台风的移动路径，故在单部雷达资料第一步反演背景场时加入模型弱约束。反演结果表明，加入模型弱约束后，反演的背景风场就能看出台风的涡旋特征，通过第二步反演后与两部雷达资料结果相近；加模型弱约束的单部雷达反演结果与两部雷达反演结果间u、v分量的相关系数均在0.8或以上，2-7 km高度层u、v分量的均方根误差明显减小。

An analysis of wind field retrieval for typhoon Bilis based on Doppler radar and its improvement

A two-step variational method is used to retrieve the “0604” typhoon (called Bilis) of 2006. The retrieval results using the single radar data were compared with that using the dual-Doppler radar data. The results indicate that the two-step variational method can not retrieve well the structure of typhoon using the single radar data. However, this method can retrieve the vortex structure of typhoon at the first step with the dual-Doppler radar data. The Rankine model and the Chen 3 model fit well within and outside the radius of the maximum tangential velocity of typhoon Bilis, respectively. The experiential symmetrical model is added in the two-step variational method in order to determine the moving path of typhoon with the single radar data. The result shows it improves the retrieval ability of the two-step variational method. The retrieval result of wind field is better at the first step by using single radar data after adding the symmetrical model and it is similar to that by using the dual-Doppler radar data. The correlation coefficients of u and v between retrieval results with the single radar data adding the symmetrical model and with the dual-Doppler radar data are both above 0.8, and the mean square errors of u and v at the heights of 2-7 km decrease significantly.