ENERGY FLUXES FROM HETEROGENEOUS TERRAIN - AVERAGING INPUT PARAMETERS OF THE PENMAN-MONTEITH FORMULA

The determination of average fluxes of latent and sensible heat is treated on a regional scale. On the basis of the linearizations used in the Penman-Monteith formula, weighting procedures for subgrid input parameters are derived for the proper calculation of latent and sensible heat fluxes. These surface parameters are albedo, soil heat Aux, surface resistance and aerodynamic transport resistance. The different weighting coefficients, depending on aerodynamic and surface resistance, are examined. For different sets of meteorological boundary conditions and subgrid properties the resulting fluxes of latent and sensible heat are compared with results of the method proposed by Lhomme (Agric. For. Meteorol., 61: 11-21, 1992). The averaging method proposed does not save computing time. However, the method is thought to be helpful for the attempt to move the averaging from the parameters of the Penman-Monteith formula back to the basic surface properties.