Continuous Measurement of Vertical Water Temperature Profile in the North Basin of Lake Biwa

Abstract

In order to examine the seasonal variation in thermal stratification and characteristics of internal waves, we made a continuous measurement of the temperature profile from top to bottom in the North Basin of Lake Biwa for more than half a year in 1992. The seasonal thermocline first formed at the end of April. However, it sometimes became unclear until early June. The secondary (temporal) thermocline developed in the epilimnion intermittently in this period. The internal seiche of the first mode occurred in the first half of May. This internal seiche was observed until the end of the observation period except for the latter part of September, but its period changed. The internal wave with a half-day period also developed intermittently in the summer and autumn. In the summer hypolimnion, this wave reached 10 m in height. Internal surges sometimes occurred in the summer.