Influence of land surface parametrizations on climate simulations at high latitudes

Analysis of long-term data records demonstrates that global warming trends have been especially large in North American high latitudes. Climate change scenarios generated using GCMs also suggest that the magnitude of future warming may be largest in high latitudes. The majority of modelling studies that have addressed future climate change in the Arctic have focused on the importance of variations in cloud cover, sea ice extent, and high-latitude oceanic circulation patterns. However, given the known importance of land-atmosphere feedbacks in the climate system, and the large land surface coverage in the Northern Hemisphere, it is likewise important to investigate the effect of land surface processes on the simulated climate.

This paper will focus on sensitivity studies that have been carried out using CLASS, the Canadian Land Surface Scheme, on land surface parameterizations in high latitudes over Canada. CLASS has been extensively developed and tested against data from Canadian field sites, and incorporates features that are particularly important for the simulation of energy and water cycles in cold regions. Among the processes that will be discussed will be the interaction of different types of vegetation with snow cover; the effect of soil type, particularly organic soils, on soil energy and water budgets; the influence of permafrost and active layer development on the surface hydrology; and the influence of slope angle and orientation on the surface energy balance at low sun angles.