Effective parameters for surface heat fluxes in heterogeneous terrain

The relations between most land-surface characteristics and surface heat fluxes are typically non-linear. Because the ground surface is heterogeneous at all scales, it is important to account for these non-linear relations. Effective parameters are often applied for that purpose. Steadystate simulations were used in this paper to thoroughly analyse the effective parameters impact under a broad range of atmospheric conditions. The effect of different types of aggregating functions on the accuracy of various effective parameters is also examined. The authors found that linear averaging of leaf area index and soil water content gives higher latent and lower sensible heat fluxes than the corresponding flux averaging over all surface types existing in one square grid. Linear averaging of roughness length under unstable conditions provides higher latent and lower sensible heat fluxes than flux averaging, whereas under stable conditions gives higher sensible and lower latent heat fluxes. Non-linear functions result to be more useful than linear functions to compute the effective value of those parameters which affect the surface heat fluxes independently of the atmospheric stability (e.g., leaf area index and soil water content,and unlike roughness length).