| Continuous Records of Water Currents in Lake Biwa (I) - Time Variation of Currents off Hikone and off Ado River - |
| Shuichi ENDOH, Iwao OKAMOTO, Reiko KISHIDA and Takahiro KIMURA |
| Suion No Kenkyu, 26-3, 35-47, 1982 |
| Continuous measurements of water currents and temperature were carried out off Hikone and off the mouth of Ado River in the north basin of Lake Biwa during 1976-1979. The data were recorded by Aanderaa current meters (RCM-4) every 10 minutes. Based on these data, some characteristics of water currents were analyzed. At every station, currents are dominant in the directions parallel to the shore line, or bottom contours, in particular, southward current is highly frequent off Ado River all the year round. Current is strongly controlled by the wind stress in winter, and good correlation was found between wind and current speed off Hikone. In the season of thermal stratification, internal wave causes a large time variation of the current velocity in both surface and bottom layers. A counterclockwise gyre is developed rapidly in May-June, and dominates the surface current in the offshore zone throughout the stratification period. It seems, however, that there exist no stable gyres in winter. Inertial oscillation is often visible off Hikone with the inertia radius of about 1 km. The land and lake breeze causes a daily variation of the surface current off Hikone, and the current direction is deflected to the right from down-wind direction. |