A re-evaluation of surface layer turbulence from Antarctic data

Abstract

A data set of velocity and temperature variances measured in the surface layer over a glacier in Antarctica is analysed in terms of the Monin-Obukhov Similarity Theory. The presence of surface inhomogeneities, flow unsteadyness, and other uncontrolled disturbances affects the shape of the distribution of normalised variances for intervals of the stability parameter. The modal value of the distribution, instead of the mean, is used to estimate the numerical coefficients of the similarity functions to minimize the influence of the (positive) outliers on the estimates. The overall agreement of the present results with previuos investigations is good, and also the spread of the numerical values noted by different authors is confirmed. In particular the investigation points out the need to use a similarity function for the temperature variance which diverges in near neutral conditions, as the heat flux goes to zero, and the occurrence of a large stability region where the variances of velocity and temperature are characterised by behaviour almost independent of the momentum flux. PACS 47.27.nb Boundary layer turbulence PACS 92.60.Fm Boundary layer structure and processes PACS 92.60.hk Convection, turbulence, and diffusion