On the mean sea levels at various locations along the coasts of Japan
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In cases covering 90% of all the tide-gauge stations, the magnitude of the annual mean rate of variation of ground level is less than 10 mm/year, and the mean value of the magnitude for all the stations is −3.17 mm/year, while that exclusive of Osaka is −1.7 mm/year.
The effect of atmospheric pressure variation on the height of annual mean sea level is of the order of several centimeters in view from both time and place.
In view of the characteristic types of variations, the coasts of Japan may be divided into five regions of similar mean sea level deviations. And in the yearly variations of mean sea levels, there can be seen a kind of variation which corresponds to the variation of oceanographical conditions such as abnormal fall of seawater temperature.
The mean sea level deviations at various locations along the coasts of Japan, referred to the standard sea level “T.P.” are different for different places. Namely, (1) on the coast of the Japan Sea, the west coast of Kyushu, the coast of Sanriku and the coast of Hokkaido, the mean sea level is higher than on the Pacific coasts from Southern Kyushu to Southern Honshu. (2) Along the coast of the Seto-Inland Sea, the mean sea level is generally higher.
As for the leading causes of the above deviations, we may safely enumerate the following ones, viz. (a) the effect of the deflecting force of the earth's rotation on currents, and (b) the effect of variation of seawater density. However, as regards the relative importance of these two effects, no decisive conclusion can yet be given for the present.
KeywordsJapan Characteristic Type West Coast Ground Level Atmospheric Pressure Variation
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