Effects of orography on Mediterranean lee cyclogenesis and its relationship to European blocking

Abstract

The role of orographically-induced cyclogenesis in the lee of the Alps in favouring the onset of Euro-Atlantic blocking is investigated by means of numerical simulations of a real case. The model used is the ECMWF global grid-point model as operational in August 1980. While the essential part that the local orography (the Alps) plays in triggering the development of cyclonic disturbances is confirmed for the first time using a global model, the relationship between Alpine cyclogenesis and European blocking remains less clear. The importance of global orography in generating and maintaining the blocking pattern is subsequently investigated and its crucial role evidenced and discussed.