单多普勒雷达资料在伴随模式同化系统中的应用研究

利用变分方法反演单多普勒雷达资料,得到风矢量场。同时,利用MM5伴随模式同化系统,结合一次暴雨过程,设计四种方案,进行数值模拟试验。结果表明,通过变分方法反演的雷达资料的应用对于暴雨的分布预报有明显的改善作用;运用伴随方法同化雷达资料后可改善对暴雨中心的预报;对于各个物理量误差的减少,雷达资料的应用也起到重要作用,尤其是对于风场作用较为明显;雷达资料的应用可加快伴随模式同化系统目标函数的收敛,得到最优初始场。

A Study of Single-Doppler Data Assimilation in Adjoint-model Assimilation System

In this context conventional and non-conventional observations(Single-Doppler Data) are assimilated by MM5 adjoint-model assimilation system so as to do research on the role of Single-Doppler Data in improving the prediction.A variational method for retrieving wind vector from Single-Doppler wind measurements is introduced and the initial forecast fields are created from the retrieved winds.Data assimilation experiments are conducted with MM5 adjoint-model assimilation system made by adjoint codes.With a case of heavy rainfall taking place from 00 h June 23 to 00 h June 24,2004,several numerical simulation experiments of different schemes are performed.The results are as follows.The utilizing of Single-Doppler data retrieved by the variational method can obviously improve the prediction of rainfall distribution.When using the adjoint-model assimilation system,the experiment adding Radar data has an improvement in predicting the rainfall centers.Furthermore,the utilizing of Single-Doppler Data plays an important role in reducing the errors of the elements,especially of winds.Besides,the use of Doppler radar data can also fasten the contraction velocity of objective function of Adjoint-model Assimilation System and the optimal initial field can be obtained.