Stability Functions for the Boundary-Layer Resistance Laws Based upon Observed Boundary-Layer Heights

Abstract

An empirical evaluation of the stability functions a, b, c and of the friction and heat-transfer coefficients is made for the modified planetary boundary layer (PBL) similarity theory which utilizes the actual height h of the PBL as the physical parameter for both stable and unstable cases. For this purpose, the Wangara data of Clarke et al. were used. In addition, the stability parameter h/L is presented as a function of the bulk PBL Richardson number and of h/z₀. It is found that both the average values of the stability functions and their scatter are comparable to those of the corresponding conventional functions A, B, C which use u_*/(|f|L) as the stability parameter. Although the results favor neither method over the other, the use of h as the physical length scale enables the external variables aloft to be evaluated at the proper height.