Fernandez, Casimiro (Dept. Geofisica y Meteorologia. Facultad de Fisica. Universidad Complutense. E-28040 Madrid, Spain)
Prego, Juan A. (same affiliation)
Summary
The development of a nearly stationary mesoscale convective system (MCS) observed near the coast of Valencia region (Spain) on November 1987 has been simulated with the UCM-PROMES limited-area model nested in ECMWF analysis. This system was characterized by its uncommon duration (33 hours) in relation to its small size (200 km max. diameter) and an impressive precipitation efficiency (>800 mm maximum local rain-fall recorded in 36 hours).
The influence of various external forcings, such as surface temperature, local orography or terrain roughness, upon the characteristics of the system is studied. This analysis makes it possible not only to identify the most important factors, but also to deduce the importance of some other internal forcings and to propose explanations for some dynamic features of the system that were difficult to understand. Hence the sensitivity test methodology applied seems to be a usefull tool to clarify the complex dynamics of some moist convective events. In the modeled MCS, sea surface temperature and orography are identify as key factors. The results also indicate that the upstream triggering of convection provoked by an orographic blocking effect is the main cause of the development of the system, while upslope triggering plays a secondary role.