The effect of typhoon on the sea level variations at three tidal stations in Pusan, Izuhara, and Hakata in the Tsushima / Korea Strait is studied by using hourly sea level data and numerical experiments. The characteristic features of the sea level variations at these three tidal stations are found to be: (1) the existence of the time-lag between the maximum sea levels at these stations (2) the persistence of the high sea level at Pusan for about a week even after the passage of the typhoon and (3) the occurrence of oscillations with a period of about 2.5 days after the passage of the typhoon. The results of the numerical shallow water experiments with the high resolution (1/12⁰ × 1/12⁰) explain well the observed features of the sea level variations at three stations above. The time-lags between the maximum sea levels are caused by the difrerent response of the sea levels at each station to the typhoon. In Pusan and Izuhara, the sea level responds isostatically to the atmospheric pressure as the typhoon approaches to these stations, while in Hakata, there develops the southwestward coastal flow which is driven by the southwestward wind accompanied by the typhoon and cancels the increase of the sea level due to the isostatic response to the atmospheric pressure by the typhoon. The high sea level at Pusan after the passage of the typhoon may be maintained by the southwestward coastal current along the south Korean coast which is driven by the large scale cyclonic eddy formed in the Japan Sea by the typhoon, although the duration in the model is shorter than the observed one. The oscillation of about 2.5 days period after the passage of the typhoon seems to be a basin scale oscillations due to the propagation of Kelvin wave generated by the typhoon.

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Source and fate of organic matter once entered to the surface water of the ocean are briefly reviewed. Phytoplankton photosynthesis and terrestrial input through the airborne and waterborne processes give rise to change the concentration of organic matter in the euphotic layer. Regional and seasonal variabilities of the concentration of the organic matter gives much influence on the downward flux of organic matter at the bottom of the euphotic layer, which is the most important factor to govern the regeneration rate of the nutrients in the aphotic layer through the decomposition of organic matter. Fate of the organic matter of the sinking particles transferred to the deep water are discussed on the basis of the vertical flux data of organic matter measured by sediment trap experiment conducted in the North Pacific.

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This report is concerned with computer graphics for three dimensional lattice data of the world ocean. As an example of such a data set we use climatological data of the world ocean by Levitus. For visualization of the data we apply hierarchical representation methods that are considered to be useful for region representation. A quadtree data structure is constructed for two dimensional representation, and an octree data structure for three dimensional one. Some examples for two and three dimensional representation of salinity distribution in the Pacific Ocean are shown. It is found that hierarchical methods are effective especially for three dimensional representation compared with a simple method without tree data structure. Further we try three dimensional representation of water temperature distribution in a region with specific salinity values by extending an octree method.

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