The impact of resolution and of MAP reanalysis on the simulations of heavy precipitation during MAP cases

Two meteorological models, operating at different horizontal resolutions up to 2.2 km, are employed in order to verify quantitative precipitation forecasts during three MAP Intensive Observing Periods, characterized by relatively high amounts of precipitation in the region south of the Alps. The recent availability of the MAP reanalysis using ECMWF 4D-Var data assimilation system allows for an assessment of its impact on high resolution forecasts in comparison with the operational ECMWF analysis (as in 1999). The evaluation is made using statistical scores generally applied to precipitation fields, introducing a smoothing criterion based on model derived probability estimates. Results indicate a generally better performance of the non-hydrostatic, high resolution, convective-resolving model in comparison with the hydrostatic, moderate resolution model with parameterized convection. The impact of the MAP reanalysis is less evident, although in one case clear improvements in precipitation forecasts are noted.