Evaluation of a 3-D hydrodynamic model and atmospheric forecast forcing using observations in Lake Ontario

Six-month observations of surface meteorology, water temperature, and currents in Lake Ontario are used to evaluate a high-resolution, three-dimensional hydrodynamic model and the forecasted forcing from a regional version of the Canadian operational global environmental multiscale (GEM) model. The hydrodynamic model is based on the Princeton Ocean Model (POM). Driven by both the observed and modeled surface wind stress and the surface net heat fluxes (SNHF), POM is able to reproduce the observed variations of the lake surface temperature (LST) and vertical stratification conditions at the seasonal and synoptic time scales. The model also has skill in simulating the temporal and vertical variation of currents. The patterns of the simulated horizontal distributions of the LST and lake circulation are consistent with the observed climatology. Model sensitivity experiments reveal that the differences between the simulations using observed and model forcing are mainly due to the difference in wind stress instead of the SNHF. Comparison with meteorological observations suggests that GEM has good accuracy in simulating the SNHF but overestimates the wind. Model sensitivity experiments further revealed that errors in the SNHF have significant impact on simulations of water temperature in the surface and near-surface layers, whereas errors in wind stress cause significant changes of water temperature in the thermocline.