Sea surface heights (SSHs) derived from TOPEX/POSEIDON (T/P, hereafter) altimeter are used together with in situ data and AVHRR IR images to investigate the ocean south of the Hokkaido Island. We processed the T/P data to derive SSH anomalies from 1-year averaged SSHs along the T/P satellite subtracks, and the SSH maps produced from the SSH anomalies and the 20-years averaged hydrographic SSH. Comparing each observation results, the oceanic conditions during October to November, 1992 are described. A mooring system with current meters was located just under a T/P subtrack. The cross-track surface current anomalies derived from T/P altimetry and observed at 138m depth by the mooring system are compared favorably with a correlation coefficient of 0.55 and a root mean square error of 7.6 cm/s. The Kuroshio Extension, the warm-core rings, and the Oyashio current are confirmed by the AVHRR images and the cross-track surface current anomalies along the T/P subtracks. On the contrary, the narrow band of the Oyashio current does not appear in the SSH maps though the Kuroshio Extension and the warm-core rings are confirmed. It is demonstrated that combination of the SSH derived from the altimeter, the AVHRR IR images and the hydrographic observation data may be a useful tool to investigate the complicated oceanic conditions formed by the Oyashio, the Kuroshio Extension and the warm-core rings in the ocean south of the Hokkaido Island.

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Yields of Hosome-konbu (Laminaria religiosa) up to 3 × 10³ t and catches of spring-spawning herring (Culpea pallasii) in excess of 2 × 10⁵ t had been landed from Shiribeshi district along the southwest coast of Hokkaido during the former half of this century. However, there is no migration of herring and yields of Hosome-konbu are on the decrease less than 10² t at present. Long-term coastal sea temperatures at Suttu in Shiribeshi district indicate a difference in sea conditions in winter between the cold-former half of this century and the warm-later. Regression of yields of Hosome-konbu (Y: t) to the variables of catches of spring-hering l year earlier (H_&lt-1&gt: 10³ t) and of favorable temperature indices (Ft) is given by Y=5.18H_&lt-1&gt+8.67Ft+579 (R²=0.80, α=0.01, Fo=73.17 &gt F=5.39). This relationship indicates possible effects of spawned eggs and sperm by herring (0.80) and the environment (0.28) upon the decreases in yields and biomass of Hosome-konbu.

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Basic concepts of the optimal interpolation method for basin-scale subsurface thermal field mapping are reviewed. The signal to noise ratio and the autocorrelation function in the analyzed hydrographic field are used as known parameters in this method. Since the accuracy of estimation of these statistical parameters has improved remarkably owing to recent international efforts to accumulate observation data, the optimal interpolation method is recently well applied to oceanographic analysis. It is emphasized that the definition of signal depends upon the temporal and spatial scales of phenomena that one interests. Distinction of signal and noise is explained by power spectrum schematically, and the methods of estimation of signal to noise ratio are demonstrated by using autocorrelation function and structure function. The calculation of the weights of the data in the interpolation is explained. And the change of weights in terms of the sampling density is interpreted. It is also shown that the interpolation error mainly depends upon sampling density, and that the optimal interpolation method is useful to design the future observation network. Advantages and characteristics of this method are discussed by compering with the other interpolation methods. Recent advanced applications of the optimal interpolation method to the thermal field mapping are reviewed.

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