Performance of two cumulus convection parameterizations for two heavy precipitation events in the Western Mediterranean

Summary A set of mesoscale numerical simulations using the Emanuel and Kain-Fritsch deep convection schemes has been performed in order to determine the sensitivity of the forecast-especially, the rainfall-to the scheme used. The study is carried out for two cases of heavy precipitation in the coastal zone of the Western Mediterranean, where the topographic forcing is of primary influence. The first one, characterized by an almost stationary synoptic situation, is dominated by warm, moist advection at low levels; the second one, of frontal type, presents a much stronger dynamic forcing at upper levels. Although the comparison attempt is conditioned by the limited number of considered cases, the numerical results provide at least some preliminary conclusions. The inclusion of a convective scheme improves the forecast precipitation, through two actions: directly, producing more realistic rainfall patterns in areas of convection; indirectly, avoiding excessive precipitation in areas with orographic or dynamical upward forcing by drying and stabilizing the atmosphere upstream. In particular, the Kain-Fritsch scheme seems to be more sensitive to the orographic forcing, in agreement with observations.With 21 Figures