Previous studies showed that the sand waves in the Bungo Channel develop in the area whose water depth is 7Om through l00m. In this study, we calculated tides, tidal currents and the residual flow in autumn 1995 by means of a three-dimensional numerical model. We examined the relationship between the amplitude of tidal currents and the existence of sauad waves, and also between the direction of sand wave migration and that of residual flow. It is found that the distribution of sand waves coincides with the area where the amplitude of tidal currents at the spring tide is between 50cm/s and 70cm/s. The direction of sand wave migration approximately coincides with the direction of residual flow. Sand transport in the Bungo Channel is mainly controlled by the tide-induced residual flow. It is supposed that sands provided from the Hayasui Strait and the northern part of Kamadozaki are transported to the shelf slope region in the southern part of the Bungo Channel.

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This study shows the route of migration of larvae of the Japanese eel, Anguilla japonica, by a numerical model. The Japanese eel has been estimated to spawn around the North Equatorial Current. The model shows the migration rout of larvae (leptocephai) from the spawning region. The model also estimates the migration rout of larvae which wrere found at the southern coast of Japan. The model was run based on the general circulation model, and lagrangean particle transport method was applied. They are estimated as follows. (l) Particles which were located between l2°N and 20°N, 13l°E and l39°E at 80m depth do not reach southern coast of Japan within 150 days, however, most of particles at 20m depth reaches Japanese coast. This suggest that larvae might migrate shallower layer in the early stage. (2) Particles which would migrate to the southern coast of Japan come from North Equatorial Current region between 15°N and 20°N, l25°E and l35°E.

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An algorithm of retrieving SST from TRMM Microwave Imager (TMI) aboard Tropical Rainfall Measuring Mission (TRMM) launched in November 1997 is developed. Root square mean of difference between monthly TMI SST and SST of the Japan Meteorological Agency is within 0.7∼0.8°C in the global ocean. TMI SST in the equatorial Pacific Ocean clearly shows a time sequential change of SST from El Nino in early 1998 to La Nina like in middle 1998. Although there remain several problems to be solved to improve an accuracy of TMI SST, such as calibration, effect of strong wind, sun glitter, et al., TMI SST will give new information about SST, from studies of comparing with infrared SST and studies of SST of quickly change.

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The tropical ocean-atmosphere is a major component of the Earth's climate system and exerts a strong influeutce on climate variability worldwide. Especially, Western Pacific Warm Pool including the western equatorial Pacific and the eastern equatorial Indian Oceans plays an important role in climate variation of the ENSO (El Nino/Southern Oscilation) and Asian monsoon. Although the tropica1 climate system has been intensively studied in recent years, very little is known about its past behavior over interatnnual and interdecadal time-scales. Well-preserved massive coral, which is composed of aragonite crystals, provides a unique opportunity for precise time-series of reconstruction of climate and surface ocean environments. δ¹⁸O in coral banding is controlled by sea-surface temperature and salinity (relative contribution by precipitation, river input and seawater). Precipitation in the western equatorial Pacific would reduce salinity, which should affccct δ¹8O in coral skeleton. Although Sr/Ca ratio in coral skeleton is good proxy for sea-surface temperature, the analysis by TIMS (thermal ionization mass spectrometer) costs too much to accoumplish many measureunents for long cores at high-resolution. Mg/Ca and/or Mg/Sr ratios may be alternative good proxies for sea-surface temperature because ICP-AES (Inductively coupled plasma - atomic emission spectrometry) and ICP-MS (Inductively coupled plasma - mass spectrometry) analyses are suitable for large number of measurements. Also trace metals to calcium ratios records offer a potential for estimating ntutrient concentration, acrosol input, upwelling and oxidation/reduction levels.

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