Numerical simulations of three MAP IOPs and associated microphysical processes

The data collected during three contrasting Intensive Observing Periods (IOPs) of the Mesoscale Alpine Programme (MAP) were used to assess the performance of the Meso-NH model with particular emphasis on precipitation and microphysical processes. The model was able to reproduce the intense and moderate convective rain of IOPs 2A and 3, respectively, and also the stratiform precipitation associated with IOP 8. Microphysical budget computations were used to derive the mean vertical distribution of the hydrometeors and to quantify the relationships among the different water species. The results of IOP 8 exhibit a shallow stratiform system in which the dominant ice hydrometeor is snow, growing efficiently by vapour deposition. In contrast, the results of IOP 2A show a much deeper system in which graupel and its associated growth modes play an important role. These results are consistent with the two conceptual models of orographic rain that were derived from the MAP radar observations