| Circular Currents in the North Basin of Lake Biwa (1) - Seasonal Variation of Circular Currents deduced from Water Temperature Distributions - |
| Shuichi ENDOH, Iwao OKAMOTO and Mamoru NAKAI |
| Japanese Journal of Limnology, 42-3, 144-153, 1981 |
| In order to examine the fluctuations of the circular currents in the north basin of Lake Biwa, successive observations of water temperature distributions using a bathythermograph were carried out from June to November, 1977. In every month, a series of measurements was made on five successive days so as to evaluate the effects of internal waves and winds on the distribution of water temperature. Assuming a geostrophic balance, velocity fields were estimated from the observed temperature fields. It has been found that (1) a large counterclockwise gyre was consistently maintained in the surface layer throughout the period of the observations; (2) there was also a virtually consistent clockwise gyre and another counterclockwise gyre was often visible in the south of a clockwise gyre; (3) internal waves and wind stresses had remarkable effects on the temperature distributions and seemingly caused a lateral movement of the gyre. It was also found that the available potential energy of the gyre was much larger than the kinetic energy, and the total energy showed a seasonal variation similar to that of the total accumulated heat in the lake. |