Simulation of alpine tundra surface microclimates using the Canadian Land Surface Scheme: II. Energy balance and surface microclimatology

Abstract

Half-hourly and daily energy balance (latent, sensible and ground-heat flux densities) output from the Canadian Land Surface Scheme (CLASS), a land-surface parameterisation scheme for use in large scale climate models, was compared with the observed microclimates of two alpine tundra sites in western Canada. Four different configurations of CLASS were employed, with varying degrees of site-specific realism. Only modest improvements over the default model performance were achieved using the more stringent configurations. CLASS successfully simulated the evaporative responses to precipitation inputs and the very rapid decline of latent heat during drying periods, both of which are signature features of the surface climatology of alpine tundra. However, daytime CLASS simulations of latent heat either overestimated or tended to zero, the latter, were occasions when simulated sensible heat flux densities exceeded measured values. CLASS modelled the surface soil moisture time series reasonably well, if a finer-textured soil was configured. Otherwise, the soil desiccated rapidly, which consequently increased the surface resistances and halted evapotranspiration. Copyright © 1999 Royal Meteorological Society