Validating Surface Heat Fluxes and Soil Moisture Simulated by the Land Surface Scheme CLASS under Subarctic Tundra Conditions

This study tests the ability of CLASS (Canadian Land Surface Scheme) to simulate sensible and latent heat fluxes, and soil moisture at two tundra sites in the Trail Valley Creek basin, Northwest Territories, Canada. These sites are underlain by continuous permafrost and feature mineral earth hummocks with organic soil in the inter-hummock zones. Two versions of CLASS were used, one with and the other without an organic soil parameterization developed for peatland conditions. CLASS was driven in a stand-alone mode and the results were compared with measurements obtained at each site during three summer months. Results from the peatland version of CLASS showed significant improvement over the standard version though both cases underestimated latent heat and overestimated sensible heat fluxes. CLASS used in this study is a one-dimensional column model and cannot explicitly represent lateral flow. The observed soil moisture content remained almost constant at both sites over the study period. As one site is in a local depression and the other at the bottom of a valley, it is reasonable to assume that the constant moisture content was maintained by lateral flow from adjacent hillslopes.