常规地面观测资料在GRAPES同化系统中的误差控制试验

利用GRAPES-3Dvar系统,分别对2004年9月3~5日、2005年7月2~4日、2008年7月20~22日的3个降水个例进行了常规地面资料各同化变量误差倍数改变的质量控制试验。结果表明,改变地面同化变量的误差倍数对进入同化系统的资料条目数是有所改变的;H的误差倍数取4时就能保证80%的资料进入同化系统,而U、V、Q的误差倍数取到2时,就能保证90%的资料进入同化系统;通过对目标函数及其梯度随跌代步数下降趋势对比分析,发现同化各变量的误差倍数取4及其以下时,其代价函数就能满足收敛条件,从而得到分析场;随着误差倍数的增加,进入同化的H资料的条目数越多,其对四川境内的降水预报的改善程度越差,而进入同化的U、V、Q条目数越多,其对四川境内的降水预报的改善程度越好,同时当误差倍数取到3以上时,各同化变量在四川境内的降水雨带与各自的误差倍数取3时一致。在既保证最大程度的利用更多同化资料,又保证其同化质量的前提下,H、U、V、Q的误差倍数的取值分别为4、3、3、3。 

Quality Control Experiments of Surface Observation Data in GRAPES 3Dvar over Sichuan Province

Quality control experiments about the surface observation data assimilation in Sichuan Province were carried out by using of the GRAPES assimilation and prediction system.0-48 hprecipitation forecasts of three heavy rainfall process that occurred in Sichuan Province at 3 September 2004, 2July 2005, 20July 2008 were analyzed.The main conclusions were as follows:Firstly, the analysis increment field were changed with the error multiple of surface assimilation variable;when the error multiple of variable H was taken 4 times, 80% data could be admitted to the assimilation system;when the error multiple of variable U、V、Q were taken 2 times, 90% data could be admitted;Secondly, from the comparative analysis results of the object function and its gradient decreased with iterative steps, they showed that when the error multiple of surface assimilation variable were taken 4 times and its under, their object functions could meet the convergence condition, then obtained the analysis field;Thirdly, the results of rainfall prediction would be worse with the error multiple of variable H increased and more H information of surface observation data assimilating;the results of rainfall prediction would be better with more U、V、Q information of surface observed data assimilating, and the prediction of rainfall band are the same with their error multiple were taken 3 times and its upper;Finally, under the condition of assimilating more surface observed data and better assimilation quality, the error multiple of variable H、U、V、Q are 4、3、3、3 times.