Mountain torque events in the Mediterranean

Abstract

Typical events of torques exerted by the Alps are analysed by correlating flow observations in the Mediterranean with these torques. More specifically, events with positive torques with respect to the "rotation axis" at 90° E, 0° N in fall are selected. A trough forms above the western Mediterranean during such an event with a ridge in the west. A separate low pressure system is induced in the lee of the Alps which moves then eastward with the upper-level trough. A linear forecast equation based on potential temperature changes reveals that this Alpine "lee cyclone" is mainly due to warm air advection east of the trough. Precipitation is discussed as well.