| Nonlinear balance constraints in 3DVAR data assimilation |
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| 摘 要： | Consideration of the so-called balance properties/ constraints is of great importance in the data assimila- tion. First, it is desirable to separate the slow modes (e.g., Rossby waves) from the fast modes (e.g., gravity waves and deep convection). Second, consideration of the balance constraints enables us to infer information about all variables that are balanced with the observed variable and hereby improve the quality of the analy- sis. The balance properties are usually represented by some…
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| 收稿时间： | 1 November 2004 |
| 修稿时间： | 7 June 2005 |
Nonlinear balance constraints in 3DVAR data assimilation |
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| Authors: | ZHU Jiang YAN Changxiang |
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| Institution: | International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China |
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| Abstract: | In many applications of 3DVAR, the balance constraints can be considered via two main approaches: weak constraint method which adds penalty terms to the cost function; and proper defi- nition of the background error covariance matrix with non-zero cross-correlation sub-matrices. The weak constraint approach requires determining the weighting matrices of the penalty terms. The background error covariance approach does not require determining those additional weighting ma- trices. However, it is only applicable to those linear or linearized balance constraints. A novel ap- proach is proposed based on the background error covariance approach by generalizing the so-called Derber-Bouttier formulation. An assimilation experiment of estimating temperature and salinity from the sea surface dynamic height observation is given to illustrate the proposed treatments of nonlinear balance constraints. |
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| Keywords: | 3DVAR linear balance constraint nonlinear balance constraint background error covariance matrix sea surface dynamic height |
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