Buzzi, Andrea (FISBAT-CNR, Bologna, Italy)
In order to understand basic meteorological processes associated with orographic heavy rainfall in the Mediterranean coastal areas, it is necessary to investigate the orographic influence on weather systems on scales ranging from cyclone scale to local mountain slope scale.
Moreover, intense rainfall is associated with moist processes and large vertical velocities that require consideration of large amplitude disturbances and latent heat exchanges.
While the effects of orography on small amplitude, dry cyclones have been already studied in several aspects, little is known about the combined effects of orography and moisture on finite amplitude cyclonic disturbances.
This problem is addressed in simplified, idealized geometry but with realistic "physics", that is using a NWP model (BOLAM) in a periodic channel configuration. The main result is that the orographic influence on the spatial structure of baroclinic disturbances is modified and, at least in some cases, enhanced by latent heat release and finite amplitude effects. On the local scale this process is associated with spatial contraction and enhancement of precipitation near one side of the orography.