OPTIMIZED COMPUTATION OF TRANSFER-COEFFICIENTS IN SURFACE-LAYER WITH DIFFERENT MOMENTUM AND HEAT ROUGHNESS LENGTHS

A new method for computing the surface transfer coefficients is propos ed, based on state-of-the-art empirical flux-profile relationships. Th e influence of the roughness length ratio is first demonstrated with t he classical iterative calculation method. Then a non-iterative algori thm is developed, taking into account the difference between momentum and heat roughness lengths. The new method is validated by comparison with the reference iterative computation. The large gain-in computer p rocessing time (CPU) time gain for the calculation of surface fluxes i n Eulerian grid models is finally assessed.