Wind profiles through boundary-layer capping inversions

Wind profiles have been measured through daytime boundary-layer capping inversions at a site surrounded by fairly flat terrain. The measurements were made by an instrument package mounted on a tethered balloon cable. Analysis of the results has shown that in the region of the inversion, the wind profiles generally show strong shears and also relatively narrow jet or minima features that vary with time. The profiles have been compared with the results of simple one-dimensional models which reproduce several of the observed features. The comparison has shown that some of these features are a result of inertial oscillations taking place in the stable layer immediately above the inversion, and suggests that the oscillations are coherent over a distance of hundreds of kilometres. Although their origin is related to that of the noctural jet, the daytime jets observed have a different structure due to the elevation of the stable layer. In particular, a narrow jet is formed when the inertial oscillation is at its minimum. This has no counterpart in the nocturnal case.