Analyses of the precipitation pattern on the Alpine region using differentcumulus convection parameterizations

The analysis of several precipitation events occurring during June 1990 in the Alpine region is performed using the Pennsylvania State University-Nati onal Center for Atmospheric Research Fifth-Generation Mesoscale Model, vers ion I. A high-resolution dataset provided by Monitoring Precipitation Activ ity in the Padana Region observational campaign (June 1990) is used to veri fy the model forecast. Comparisons between model simulations, using different cumulus convective s chemes associated with tither an explicit computation of cloud water and ra in (EXP) or a nonconvective scheme (NEXP), have been performed. The compari sons of EXP versus NEXP give indications of the ability of a cumulus scheme to handle nonconnective precipitation. On the Ether hand, comparing the sc hemes allows for evaluation of the ability to reproduce total and convectiv e precipitation The results show that the amount and the areal extent of th e total precipitation are well reproduced if a cumulus scheme is associated with EXP; the differences between the simulations performed using EXP and NEXP are reduced if the precipitation is driven by a strong large-scale for cing such as a front. The comparison of the cumulus convection parameteriza tions highlights the different responses of the schemes to the meteorologic al situation. When the explicit computation of cloud water and rain is used , a good localization of the rain cells and a fair estimation of the amount of precipitation are obtained using either the Kain-Fritsch or the Grell c umulus convection parameterizations. On the other hand, the Anthes-Kuo sche me produces a strong overestimation of the precipitation regardless of the meteorological forcing and with both EXP and NEXP. The bias and the threat score for the cases analyzed confirm this finding. Sensitivities to different initial conditions for the same case show that t he precipitation forecast depends on the strength of the signal contained i n the initial conditions.