水温変動からみたびわ湖の内部波の研究

Abstract

In order to reveal the time variations of water temperature field in the north basin of LakeBiwa, successive measurements of spacial temperature distribution were carried out using a bathy-thermograph for four days during 28-31 August, 1973. The horizontal distribution of observedwater temperature at the thermocline depth fluctuates largely day by day. This fluctuation seemsto be caused by the rotating internal wave, which has been pointed out by Kanari.At the fixed buoy station, Ie-1, time series of current and water temperature were obtained.Results show that the internal wave with the period of about 40 hours has been dominant in thefluctuations of both current and water temperature. An elliptical hodograph of this wave hasbeen obtained and this means the Coriolis' force plays a very important role to the internal waveof the fundamental mode. It is interesting that the direction of the major axis of the ellipsealmost coincides with that of the longitudal line of Lake Biwa at this buoy station.