MODELING THE THERMO-HYDRODYNAMICS OF A SHALLOW BOREAL LAKE: 3D MODEL VERIFICATION

Abstract

3D modelled results were verified against observed data obtained along three transects in a shallow boreal lake Vendyurskoe several times during the ice season. It was revealed that 1) the model overestimates ice thickness; at the same time, modelled ice-on and iceoff dates are very close to those observed; 2) in general, the model underestimates the water temperature by 8–10 %; 3) comparison of modelled currents with observed data on mean currents revealed qualitative compliance of current direction (coincidence of quadrants) and modulus of velocity (coincidence of the order of magnitude and a slow decrease of velocity over time during the ice season 1994–1995). Underestimated water temperature may affect the quality of simulation of chemical-biological processes. For instance, one may expect overstated absolute values of dissolved oxygen content in the bulk of the water column. Overestimated modelled water temperature for layers near the bottom of local cavities may influence the rates of the chemical-biological processes occurring there. Despite the model errors found in the course of verification, the model quite realistically describes the hydrodynamic processes in a shallow ice-covered lake, and can therefore be regarded as a useful tool for further research after the diagnosed defects are removed from the computer code. As an option of the code improvement, the authors consider further elaboration of the module of heat/salt flux to/from bottom sediment, development of parameterisations facilitating heat transfer along the water column on sub-grid scale.