The tidal current in Kagoshima Bay is simulated by the two-dimensional subdomain finite-element method. At the open boundary, the sea level is forced to be oscillatory with a linear combination of the four harmonic constituents (M2, S2, K1, O1) of the tide. A calculation having only M2 sea level at the open boundary is also performed and the harmonic constants of M2 are compared with those calculated by the four components.
In the calculated velocity vector, a large difference between the two maxima or the two minima in one day appears when the vector is directed to the open sea. On the other hand, when it is directed into the bay, the two extreme velocities are almost equal. In tide-killer residual flow, the flow pattern is almost independent of the tidal age; however, the absolute value of the current velocity depends on the tidal age. The pattern is nearly the same as that calculated by giving only M2 sea level at the open boundary.
In relation to the nonlinear interaction, the kinetic energy ratio KER is defined. by the ratio of kinetic energy of the induced harmonic components to that of harmonic constituents given at the open boundary. KER is large where the tidal current is disturbed by obstacles, e. g. along the west coast at the mouth of the bay and in the southern sea of Mt. Sakurajima. The distribution of KER seems to be independent of the number of harmonic constituents (one or four) given at the open boundary. The difference of kinetic energy of the M2 tidal constituent between the two calculations. i. e. with the open boundary conditions of four components (M2, S2, K1, O1) and of a single component (M2), is found to be large where the current velocity is large.

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Current measurements were made at five moored stations over the continental shelf off the San'in coast of the Japan Sea for a month in the summer of 1980 to study the vertical structure of the nearshore branch of the Tsushima Current. The time-mean current for the observational period is 20 to 25cm sec^-1 eastward near the surface and about 10 cm sec^-1 westward near the sea bottom except at the shallowest station. The time-mean current, i.e. the nearshore branch of the Tsushima Current is mainly due to the baroclinic modes. The currents are less variable in the first half of the observational period, but fluctuate with a several-day period in the latter half. The obtained current data were decomposed into barotropic and baroclinic modes to investigate the detailed characteristics of the fluctuations. In the latter half, the current fluctuations of the two modes with about a 5-day period are well correlated with each other, as the baroclinic mode lagging behind the barotropic mode by 12 hr. The barotropic current fluctuation is correlated to the sea level, with the former leading the latter by about 12 hr. The baroclinic current is correlated to the temperature at the subsurface layer with a shorter time lag.

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Hydrographic casts down to the bottom along two zonal sections at 12°N and 13°N (from 144° to 127°E) were made with a CTD. Their analysis verified the existence of cold and saline abyssal water between the Mariana Ridge and the Kyushu-Palau Ridge. This result provides evidence of flow into the Philippine Sea through the deep gap called the Yap-Mariana Junction. The properties of deep water are variable in the West Mariana basin but quite homogeneous in the Philippine Basin, indicating the transitional nature in the West Mariana Basin and the existence of older bottom water in the Philippine Basin. A close examination suggests that the bottom water is slightly colder in the western part of the Philippine Basin than in the eastern part of the basin. This slightly colder deep water with a hundred kilometer scale in the western Philippine Basin might be related to a broad western boundary current flowing equatorward along the eastern rise of the Philippine Trench.

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Analysis is made of wind and wave data, which were obtained during the passage of Typhoon 8013 at an Ocean Data Buoy Station south of Honshu operated by the Japan Meteorological Agency, in order to investigate the wave dependence of sea-surface roughness parameter in the situation where wind waves are dominant with less significant swells. The data fit better the wave-dependent expression of the wind stress, z₀σ_p/u=γ, than to Charnock's formula, gz₀/u²=β, where z₀ is the roughness length, σ_p the angular frequency of the spectral peak of wind waves, u the friction velocity of air, g the acceleration of gravity, γ and β are non-dimensional constants. The results are very similar to those of our previous study using data from an oil producing platform in the Bass Strait, Australia, although the type of observation system and the synoptic situation of the winds and wind waves were totally different.

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Cell densities of phycoerythrin-fluorescing cyanobacteria and other chlorophyll-fluorescing picophytoplankton in the 0.2-2.0μm size fraction were investigated, using an epifluorescence microscope, in the western North Pacific Ocean (36.5-44.0°N, 155.0°E) in the summer of 1989. Cyanobacteria were most abundant in the surface of the subtropical water (36.5-38.0°N) and less in the northern sea area (39.5-44.0°N). The cell density of other picophytoplankton was, however, high in the northern part and low in the subtropical water. Results showed that algae other than cyanobacteria may significantly contribute to the picophytoplankton community under the low water temperature conditions of open waters. Chlorophyll α concentration represented well the abundance of picophytoplankton other than cyanobacteria, but had no significant correlation with the cyanobacteria cell density. Chlorophyll α-based data must be interpreted with caution, since the abundances of cyanobacteria were often considerably different even though the chlorophyll α concentrations were the same level.

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Non volatile N, N-dimethylformamide (DMF) at room temperature is proposed as a new solvent for determining the chlorophyll α in cultured and natural phytoplankton samples. Advantages of DMF compared to the solvents ordinarily used are (1) higher extraction efficiency, (2) rapid extraction time of 30 min, (3) simple extraction procedure requiring neither extra heating nor grinding, but soaking, and (4) a long stable life of chlorophyll α(at least one month at 5°C in the dark).

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