Examination of a Wind Profile Proposed by Swinbank

Abstract

Micrometeorological measurements made during Project Prairie Grass have been used in an examination of a theoretical model proposed by Swinbank to describe wind speed profiles in the lower portion of the atmospheric boundary layer during conditions of non-neutral temperature stratification. In the derivation of the Swinbank hypothesis the Monin-Obukhov length, L, is employed. The derivation depends upon an assumption that L is constant in the lower boundary layer. The analysis of the observational data, however, reveals a systematic increase of 1/L with height during lapse conditions and a systematic decrease of 1/L with height during inversion conditions. Unsuccessful attempts to explain these variations of 1/L with height are discussed. It is concluded that the Swinbank hypothesis is not verified by the micrometeorological data of Project Prairie Grass.