初始场的同化对短期气候预测的影响

基于已建立的三维变分资料同化系统(3D-VAR),利用大气环流模式(IAP9L2°×2.5°-AGCM),对同化和未同化2种初始场分别进行了17a(1988—2004年)的集合回报试验,并对试验结果进行了相关分析.结果表明:在热带地区,2组初始场下的集合回报结果差别很小,除热带外的中高纬地区差别较大,尤其是东亚地区;另外,大部分物理量场的17a异常空间相关系数的均值在同化后的初始场下也得到了提高,可能是因为同化的初始场包含了一段时间的大气信息,动力模式更加协调.

The effect of the initial conditions after data assimilation on short-term climate prediction

Two numerical experiments of ensemble hindcasting for 17 years are performed with five-member ensembles in each experiment,and the initial conditions are NCEP-DOE Reanalysis 2 data(adopted in real-time prediction)for experiment 1 and supplied by the system of three-dimensional variational assimilation(3D-VAR)for experiment 2.The model used here is a grid-point Atmospheric General Circulation Model with 9 vertical levels and a resolution of 2°in latitudinal and 2.5°in longitudinal direction,which is developed by the Institute of Atmospheric Physics,the Chinese Academy of Sciences(IAP9L2x2.5-AGCM).The technique of Correlation Analysis is applied.Comparison results show that(1)the difference of temporal anomaly coefficient between experiment 1 and 2 is very small in tropics,whereas it is large in middle and high latitudes,especially in East Asia(China),(2)temporal anomaly coefficient of most variables in experiment 2 is bigger than that in experiment 1 in most of China region,(3) spatial anomaly correlation of many variables have some improvement by use of the initial conditions after data assimilation(in experiment 2),due to the inclusion of atmospheric information for some time and the resulting coordination with dynamic model.The results demonstrate quantitatively that the role of the initial conditions on the shortterm climate prediction in East Asia is more important than in the global,what''s more,the initial conditions after data assimilation are better than that used in real-time prediction to some extent.