Modelling of the flow of stable air over a complex region

Abstract

The flow of stable air over a general region of complex topography and non-uniform surface temperature has been investigated. In order to gain further understanding of the motion of surface air, it was necessary to study the vertical structure of the wind for stable air moving on a slope. A theoretical model is proposed to describe the vertical structure and this was found to be in reasonable agreement with experimental data taken at Richards Bay. From this study it was concluded that the Coriolis force and rate of downward momentum transfer from the overlying geostrophic wind could be neglected in the surface air layer, and air motion is determined primarily by the distribution of surface pressure and the topographical relief. A surface wind field model is proposed, based on the above findings and the continuity equation. Inputs for model computations are topographic coordinates, land and sea temperatures, temperature inversion strength and the prevailing synoptic pressure gradient. The model includes two constants, which were empirically determined. The computed wind fields were found to be in good agreement with wind field data taken at Richards Bay.