Diagnostic analysis of water circulations in Lake Biwa
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A diagnostic model is developed for the study of steady water-circulations during summer in Lake Biwa. The most characteristic feature of the present model is to include the vertical friction terms in the basic equations, so that it is not necessary to assume a level of no-motion. Under no-wind condition, the velocity field is calculated from the density field obtained by successive observations of water temperature using a bathythermograph.
The comparisons of the present calculation with a dynamical calculation and direct current measurements indicate that the present model surpasses a dynamical calculation in the respects that 1) vertical circulations can be estimated and 2) the flow pattern in the deep layers can be obtained more reliably. One of important results of the present calculation is that a large vertical circulation has been found accompanied by the large counterclockwise gyre in the north basin. Preliminary results of direct current measurements by cross-boad drogues also seem to suggest the existence of the circulation.
KeywordsWater Temperature Velocity Field Flow Pattern Present Model Deep Layer
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