Development of Data Assimilation Methods for Mesoscale Processes and General Circulation in the Ocean

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1995-96Since data assimilation is a new approach for revealing oceanographic processes, it was extremely useful for the principal investigator (PI) and the co-investigators (CI) to exchange the information that they had among them. Hence, we held a meeting in Tsukuba in July, in which the other researchers were also invited and worked together to review the existing methods and search data sets.The PI visited Canada and did Research on the adjoint equation method taht Russian CI (living in Canada) developed. They visited Japan for one and half months to participate in the PI's projects. They visited many research institutes in Japan and exchanged their knowledge with Japanese scientists. The PI and Russian CI submitted a paper to Journal of Oceanography. One CI (Kamachi) visited Norway to investigate the Kalman filter method. This trip was highly necessary, because there was no specialist in Japan in this field.1996-97Following the first meeting in the first year, we held the second, m … More ore international meeting in Mutsu by inviting five CI from various countries. The total number of the participants wa more than 40. The participants exchanged the information on the more advanced methods of data assimilation than the first year. Some suggestions include (1) in the adjoint method, a dynamical model with a simpler physics may be more suitable as a constraint model, and (2) in the Kalman filter method, it is necessary to remove instability when a strongly nonlinear system is dealt with.The PI visited University of Hawaii to exchange information on data assimilation for general circulation in the North Pacific.Outcomes from this projects are(1) it is possible to reconstruct subsurface field from satellite altimeter data using the adjoint method,(2) it is possible to reconstruct shelf circulation from surface velocity data,(3) it is useful to include both altimeter data and drifter data to reconstruct large scale circulation,(4) it is possible to reconstruct the oceanic field beneath the surface mixed layr by assimilating surface data.The objectives initially listed in the proposal have been achieved. The information exchange was extremely useful for the PI and CI to develop their research at the initial stage. Less