Abstract
Seasonal change of the internal seiches' period will be treated by the spectrum analysis of the continuous temperature records which were obtained from the thermistor-buoy stations in Lake Biwa.The dominant period almost coincides with theoretical one which can be derived from a longitudinal internal seiche in a two-layered rectangular lake, but the observed spatial phase difference and amplitude cannot be explained reasonably by the concept of a simple longitudinal internal seiche. They rather correspond to the rotating internal KELVIN wave, which was found out from the numerical experiments in the preceding paper (6).
The results of the “Round Cruise Survey” of the thermocline of Lake Biwa, which was carried out during the period from Aug. 9 to Aug. 13, 1973 shows that the dominant internal oscillation has a rotatory nature, that is, the high water region rotates along the lake shore in the anticlockwise direction with an apparent phase velocity of 2.2km/hr (in August). Such a rotatory behavior of the internal oscillation enables us to interpret reasonably the results of the spectrum analysis of the temperature records.
