Data assimilation experiments are conducted with the MM5 adjoint-model assimilation system made by adjoint codes.With a case of heavy rainfall occurred on 23 and 24 July 2002,several numerical simulation experiments with different schemes are performed.The results indicate: the MM5 Adjoint-model Assimilation System can not only improve the initial field effectively and promote the coordination with the model but also enhance precipitation and other elements' forecasts;the assimilation of cloud-derived wind(CDW) can improve the quality of upper-level winds;the effect of direct numerical simulation with CDW to improve the initial field is better than that without CDW;when using the adjoint-model assimilation system,the experiment adding CDW can directly improve the wind forecast,but comparing that without adding CDW,there is no obvious improvement over other elements' forecasts.