抄録
Variations in oceanographic conditions of the Kuroshio (a warm ocean current) observed in Zunan sea region have an important bearing upon the oceanographical conditions and fisheries off the coast of Sanriku as well as in Zunan sea region. For this reason, the oceanographical observations in this region have been held from time to time by the Section of Oceanography, the Tokai Regional Fisheries Research Laboratory since January 1950, During four cruises in March, April, May and July 1950, the sectional observations were carried out in an area off Nojima-Zaki, extending from Sunosaki to Hachijo Island. Vertical distributions of water temperatures determined by the observa-tions reveal that a boundary area between the warm-water mass ot the Kuroshio and the cold-water mass of the Oyashio (a cold ocean current) is always outstanding and relatively stationary. It is supposed that stationariness of the boundary area is mainly caused by infusion of the Oyashio system which flows down southward along the Pacific coast of Japan.
With this view in mind the author reduced the equation of diffusion:
∂T/∂t=∂/∂χ(Aχ∂T/∂χ)+∂/∂y(Ay∂T/∂y)+∂/∂z(Az∂T/∂z)-u∂T/∂χ-υ∂T/∂y-ω∂T/∂z
to the following approximate simplified equation
l/tn+1-tn[T2, n+1+T1, n+1/2-T2, n+T1, n/2-(ΔT)S.V.]=-(A/l)[T2, n+1+T2, n/2-T1, n+1+T1, n/2].
In addition to this equation some assumptions have been introduced into consideration so as to estimate the horizontal diffusivity, A, in the boundary area and the flowing velocity of the Oyashio system. The present study is intended to provide an approach towards enlightening the variations in oceanographic conditions of the Kuroshio in Zunan sea region.
