Aggregation of energy balance controlling parameters over heterogeneous landscape

Addresses the problem of estimating surface fluxes at large scale over heterogeneous terrain, and the corresponding determination of effective surface parameters. The strategy explored is based upon the principle of flux conservation, which stipulates that the average flux over a large area is simply the area weighted mean of the contributions from the different patches making up this area. The authors show that the application of this strategy leads to different aggregation procedures for the energy balance controlling parameters, depending on the type of flux (latent heat, sensible heat or available energy). The effective value of a given parameter is not unique, but differs according to the magnitude to preserve. Numerical simulations are carried out to test over contrasted areas the aggregation procedures obtained. They prove to be more accurate to estimate the areal fluxes and to close the energy balance equation than those based upon a simple areal averaging of the parameters