Dynamics of Large Polymictic Lake. II: Numerical Simulations

The internal dynamics of Clear Lake, California-a large, multibasin and polymictic lake-are examined using simulations conducted with a three-dimensional (3D) hydrodynamic model. The model is based on an accurate and efficient semi-implicit finite difference algorithm for the hydrodynamic equations, that has been previously subject to extensive verification with analytical test cases. The high level of agreement-without extensive calibration-between the model results and the observations at several locations in the lake is comparable with previously published 3D modeling results. The model results confirm the baroclinic-pumping model of circulation proposed for the Oaks Arm of Clear Lake in Part I. The simulations show that the interaction of stratification, periodic wind forcing, and Coriolis effects drive this circulation. The diurnal readjustment of the circulation from being wind driven to baroclinically driven is examined and shown to vary spatially. This transition in circulationtype has a wavelike nature, with a distinct frontal structure and converging currents at the surface. Asymmetries in the forcing and response, combined with rotational effects, impart a cyclonic residual circulation on the flow.