Modification of blending procedure in a proposed new PBL Resistance Law

Walmsley's (1992) proposal for a new PBL Resistance Law required blending between surface- and matched-layer logarithmic velocity profiles. Here it is suggested that blending should be restricted to the matched layer, in contrast to Walmsley's original formulation in which blending was done in the surface layer. This modification does not have any noticeable effect on the wind speed profile and only minimal impact on the wind shear, but it yields more realistic profiles of wind direction. In particular, all the adjustment of wind direction takes place above the surface layer.