Newsletter No.6 March-1999

Dr.Tsuyoshi Wakamatsu

Hello there! My name is Tsuyoshi Wakamatsu, and I have been participating in the IARC since May 1998.My specialization is physical oceanography. In my student years, my subject of research was to develop an estimation technique for potential vorticity distribution caused by meso-scale eddies at the surface of ocean, using an invariant-core vortex model derived from a quasi-geostrophic equation. In this research, I have utilized a data assimilation scheme with use of an adjoint equation, based on the variational method, and have indicated that in the case of a small number of observation, this technique is more efficient in estimating oceanographic structure.

In general, the data assimilation is a technique to estimate a physical quantity with its error distribution, by using the optimal blending of data and corresponding model, both containing errors. In the physical oceanography, research in that technique has rapidly progressed over the past ten years, taking advantage of the increased supply of satellite observation data. I think hereafter the development of this technique will break new ground toward quantitative monitoring of a physical quantity concerning mesoscale phenomena, which have a spatial scale of internal deformation radius and a time scale of several weeks through several months. I also suppose that it is highly possible to apply the technique to ocean at the polar region, for which high-resolution satellite observation data, such as SAR are supplied.

In the research at the IARC, using the data assimilation technique, the focus may be placed upon how to extract dynamical information from satellite observation data including various physical characteristics of sea ices, which do not exist in the mid-latitude sea area.

At present, the research is prepared, aimed at the establishment of a estimation method of surface currents in the Marginal Sea Ice Zone, with the use of ice-drift data. In future, I would like to investigate a quantitative estimation of heat balance at surface of the marginal sea and coastal sea in the polar region, together with the development of estimation techniques of the ocean mixed layer structure including sea ices.

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