EVALUATION AND MODEL IMPACTS OF ALTERNATIVE BOUNDARY-LAYER HEIGHT FORMULATIONS

We study bulk formulations for the boundary-layer height which are cur rently in use for atmospheric modelling. The formulations are based on various forms of the Richardson number, and these are evaluated with Cabauw field data in stable conditions. Results for both a large-eddy simulation model and an E-epsilon turbulence closure model for neutral boundary layers are also utilised. An updated formulation is introduc ed, which combines the effects of shear in the outer region of the bou ndary layer with surface friction. The updated formulation has a bette r performance for neutral boundary layers with upper level stratificat ion. The findings are illustrated with a single-column model for a cas e with relatively high winds over the tropical ocean including shallow cumulus convection, and for a case with fair weather over land. We al so show that for stable conditions, the updated formulation performs b etter than estimates on the basis of surface friction alone.