On the Similarity Functions A, B and C of the Planetary Boundary Layer

Abstract

The similarity functions A, B and C are computed based on the various scales previously proposed for wind, temperature and height in the planetary boundary layer. The vertically averaged geostrophic wind recently proposed by Arya and Wyngaard is found to be a better choice as a wind scale for the Wangara experiment than a local wind at a specified height. A similar conclusion is drawn for the temperature scale. As for the height scale the similarity functions A, B and C scaled by the height of the surface inversion layer during the nighttime resulted in relatively less scatter than those scaled by u*/|f|. Nomograms for the geostrophic drag and the beat transfer coefficients are presented by utilizing the approximate expressions for A, B and C deduced from the Wangara data. Agreement between the values predicted and those deduced from the data appears to support the appropriateness of the present choice of the scales originally suggested by Arya and Wyngaard.