Orographic ciclogenesis in a saturated atmosphere and intense precipitation: baroclinic modal solutions under the joint action of localized mountains and humidity

In this paper we analyse the nature of orographic cyclogenesis in a saturated atmosphere by means of a simplified model based on the analysis of linear modal solutions. The space structure of fastest growing modal solutions suggests that three different scales of extratropical atmospheroc motion may simultaneously be activated in a single, growing, unstable mode: the orographic modulation of graowing baroclinic modes extending, as we know from the classical model theory of origraphic cyclogenesis, from the scale typical of the primary extratropical cyclone to the scale of the secondary orographic cyclone, is also characterized by the (smaller) scale associated with the strong ascending motion in a saturated atmosphere. Since ascending motion can be associated with intense precipitation, the result is important in view of its potential consequences both on the ability to achieve a good forecast of intense precipitation events in the Mediterranean and on the refinement of the theory of orographic cyclogenesis.