HR: 0800h
AN: NG31A-0846    [Abstracts]
TI: Application of ensemble Kalman filter to coupled atmosphere-ocean model
AU: * Ueno, G
EM: gen@ism.ac.jp
AF: The Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, Tokyo, 106-8569 Japan
AU: Higuchi, T
AF: The Institute of Statistical Mathematics, 4-6-7 Minami-Azabu, Minato-ku, Tokyo, 106-8569 Japan
AU: Kagimoto, T
AF: Frontier Research System for Global Change, 3173-25 Showamachi, Kanazawa-ku, Yokohama City, Kanagawa, 236-0001 Japan
AU: Hirose, N
AF: Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka, 816-8580 Japan
AB: We apply the ensemble Kalman filter (EnKF) to the coupled ocean-atmosphere model by Zebiak and Cane (ZC model, Zebiak and Cane [1987]) in order to assimilate the TOPEX/Poseidon sea surface height (SSH) observation. Since the ZC model includes several nonlinear processes, it is impossible to use the standard Kalman filter and smoother algorithms. We therefore employ the EnKF in which the Kalman gain is approximately estimated by many realizations of the state vector. Here we add process noise to the bulk formula that converts the atmospheric wind into the windstress on the sea. The filtered SSH roughly appears similar to the observation, but it is contaminated by a false stripe structure near the eastern boundary. The false stripe then propagates westward to make the model prediction get worse. This stripe is caused by the specified eastern boundary condition that induces an extremely large Kalman gain there. To avoid the contamination, we propose alternative filtering schedules in the coupled process and a possibility of another filtering method.
DE: 4504 Air/sea interactions (0312)
DE: 4522 El Ni¤o
DE: 3220 Nonlinear dynamics
SC: Nonlinear Geophysics [NG]
MN: 2004 AGU Fall Meeting