Based on the system of three-dimensional variational assimilation (3D-VAR), the numerical experiments of ensemble hindcasting for 17 years are performed in East Asia in this paper. There are two groups of experiments, the initial conditions are supplied by the system of 3D-VAR in the first group experiment and that in the second are NCEP-DOE Reanalysis 2 data. The experiments use the model which 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, developed by the Institute of Atmospheric Physics, the Chinese Academy of Sciences (IAP9L2×2.5-AGCM).The technique of Correlation Analysis is applied. Comparison results show that anomaly correlation coefficients of most variables (for example, geopotential height and temperature, etc) are larger in the first experiment not only in the mid- and upper troposphere, but also in lower troposphere. This is an indication that initial conditions provided by 3D-VAR may include more information, What's more, they may be corresponded to dynamical model.
In this study, a scheme of three-dimensional variational data assimilation (3D-Var) is introduced for a grid-point
Atmospheric General Circulation Model, developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS-AGCM). The scheme adopts stream function, unbalanced potential velocity, unbalanced geopotential height and relative humidity as analysis variables which are independent of each other. In order to avoid the complexity of background error covariance (B) and reduce the tremendous cost of minimization, variable transform and
Conjugate-Gradient Method are used here. Meanwhile, a relationship among multivariable is considered. To test the validity of system and dynamical constraints between mass field and wind field, many experiments including single observation and continuous assimilation added in model are performed, The results show that the relationship among multivariable is reasonable and improvement because of the assimilation is obvious.
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