Regional Atmospheric-Oceanic Climate Modeling over Eastern Canada

In recognition of the importance of interactions in the atmosphere-ocean-ice system and understanding the regional climate, climate variability and climate change, we are using the Canadian Regional Climate Model (CRCM) coupled with a regional ocean-ice models for the Estuary and the Gulf of St-Lawrence (GSL), Canada, to understand these interactions and their impact on the climate of eastern Canada. By resolving details in the SST and ice fields, the surface heat fluxes, connective precipitation and mesoscale circulation patterns may be significantly modified. Sea-ice dynamics is an important part of climate modeling strategies, especially in the GSL where the combined effect of tidal action and winds may produce ice velocities up to 5m/s and large areas of open water. The open leads may increase locally the sensible heat flux up to 800W/m2. Preliminary results show that the regional climate near the GSL is more vulnerable to ice conditions than SSTs. Reduced sea ice concentration in the GSL produces locally increased precipitation up to 10cm/day. This response of the coupled system is in agreement with observations.

The problem of coupling atmospheric and ocean-ice models is mainly a problem of exchange of momentum, heat and water mass between the systems via fluxes of these quantities at the interface. The vertical fluxes at the interface ocean-ice and atmosphere control the climate of both the ocean surface layer and overlying atmosphere. Because of simplifications, inadequacies or limitations of the formulation of both atmospheric and ocean-ice models, the surface fluxes are not consistent between the models. Different coupling strategies are applied over a seasonal cycle to determine the degree of adjustment that is needed to ensure a proper balance of the interacting components.