An orographically split mixed-layer and the alpine low-level jet

Summary A study is undertaken of the semi-geostrophic flow of shallow water incident tangentially upon a sharp leading edged, slender, orographic feature. The nature of the response is shown to depend upon the Froude number of the upstream flow and upon the orographic shape. In particular it is deduced that the orographically split flow has a laterally asymmetric response, and that for sub-critical upstream settings a jet can develop on one particular side of the orography. Features of an easterly low-level jet observed on the Alpine northside during the ALPEX project are compared with the theory.With 5 FiguresJosef Horn died in an Alpine accident in September 1987.