Abstract
The empirical determinations of the similarity functions of geostrophic drag and heat transfer relations by Zilitinkevich and Chalikov (1968) and by Clarke (1970a, b) indicate large disparities between their results, raising serious doubts on the universality of these relations. Some reasons for these large differences are investigated by reanalysing the available data from the two sites (O'Neill in Nebraska, U.S.A., and Hay in New South Wales, Australia) in the same format, using the best available fluxβprofile relations and reasonable criteria for the selection of suitable runs. Although there is still considerable (but, much less than in previous studies) scatter of data points, when plotted in the similarity framework, we find no significant differences in the results of two sites. Thus a large part of the above noted disparities must have been spurious, probably caused by different ways of determining surface fluxes and of defining external variables by the previous investigators.
Our empirical results are compared with those obtained from recent theoretical models for both stable and unstable boundary layers. Having fitted some third degree polynomials through the same, nomograms are obtained for geostrophic drag and heat transfer coefficients and also for the surface crossβisobaric angle as functions of dimensionless parameters defined in terms of easily measured βexternalβ variables. These show expected trends with stability.