A Note on the Boundary Layer Wind Structure Above Sloping Terrain

Abstract

The role of topography in the mean structure of low-level winds is investigated. Because the gravitational force vector has a component locally parallel to the sloping terrain, the low-level temperature anomaly, created by the necessary thermal adjustment of the air stream to a fixed ground temperature, results in an Archimedean effect in the Ekman layer. Thus, the viscous boundary layer and the thermal boundary layer are coupled. A set of three second-order differential equations which approximately governs the dynamics of the thermal-viscous boundary layer is solved. It is shown that topographical features can account for the overall spatial distribution of the wind structure in the southerly flow over the Great Plains and over Kenya. It is also shown that such a boundary layer can provide a low-level convergent environment which is conducive to rainfall activities.