Modelling fluxes of momentum, sensible heat and latent heat over heterogeneous snow cover

A boundary‐layer model is used to simulate turbulent fluxes of momentum, sensible heat and latent heat over heterogeneous surfaces. Results for heterogeneous snow cover are compared with results for heterogeneous snowfree vegetation, and effective parameters characterizing the surfaces are discussed. A tile model, which calculates area‐average fluxes from given area‐average windspeeds, temperatures and humidities at a reference height in the atmosphere, is assessed in comparison with the boundary‐layer model. the performance of the tile model is found to be degraded for surfaces with regions of both upward and downward sensible‐heat flux, as can occur over heterogeneous snow cover. Better results can be obtained by using different reference heights for heat flux and momentum flux calculations.