Application of the Canadian Regional Climate Model to the Laurentian GreatLakes region: Implementation of a lake model

This study reports on the implementation of an interactive mixed-layer/ther modynamic-ice lake model coupled with the Canadian Regional Climate Model ( CRCM). For this application the CRCM, which uses a grid mesh of 45 km on a polar stereographic projection, 10 vertical levels, and a timestep of 15 mi n, is nested with the second generation Canadian General Circulation Model (GCM) simulated output. A numerical simulation of the climate of eastern No rth America, including the Laurentian Great Lakes, is then performed in ord er to evaluate the coupled model. The lakes are represented by a "mixed lay er" model to simulate the evolution of the surface water temperature, and a thermodynamic ice model to simulate evolution of the ice covet: The mixed- layer depth is allowed to vary spatially. Lake-ice leads are parametrized a s a function of ice thickness based on observations. Results from a 5-year integration show that the coupled CRCM/lake model is capable of simulating the seasonal evolution of surface temperature and ice cover in the Great La kes. When compared with lake climatology, the simulated mean surface water temperature agrees within 0.12 degrees C on average. The seasonal evolution of the lake-ice cover is realistic but the model tends to underestimate th e monthly mean ice concentration on average. The simulated winter lake-indu ced precipitation is also shown, and snow accumulation patterns on downwind shores of the lakes are found to be realistic when compared with observati ons.