Application of the Canadian Regional Climate Model to the Laurentian Great Lakes Region: Implementation of a lake model

Abstract

This study reports on the implementation of an interactive mixed-layer/thermodynamic-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 min, is nested with the second generation Canadian General Circulation Model (GCM) simulated output. A numerical simulation of the climate of eastern North America, including the Laurentian Great Lakes, is then performed in order to evaluate the coupled model. The lakes are represented by a "mixed layer" model to simulate the evolution of the surface water temperature, and a thermodynamic ice model to simulate evolution of the ice cover. The mixed-layer depth is allowed to vary spatially. Lake-ice leads are parametrized as 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 Lakes. When compared with lake climatology, the simulated mean surface water temperature agrees within 0.12°C on average. The seasonal evolution of the lake-ice cover is realistic but the model tends to underestimate the monthly mean ice concentration on average. The simulated winter lake-induced precipitation is also shown, and snow accumulation patterns on downwind shores of the lakes are found to be realistic when compared with observations.