Some factors in the design of a regional prediction model: an examination based upon two MAP events

Abstract

Consideration is given to the impact of both synoptic-scale flow features and different model configurations upon the performance of an Alpine-encompassing regional NWP model. The so-called regional LM forecast model is used to simulate two events selected from the Mesoscale Alpine Programme (MAP), and simulations are undertaken with: different domain sizes (at 7 km resolution); lateral boundary data supplied from two data sets (the ECMWF's operational and MAP Reanalysis fields); and an embedded domain (at 2 km resolution). Quantitative evidence is provided showing (a) the specification of the incident and evolving synoptic-scale flow can exert a major impact upon the quality of the resulting simulations; (b) the simulation of the low-level meso-α scale features of the flow is helped considerably by the refined MAP Reanalysis data set; and (c) the simulated meso-β scale precipitation distribution displays some skill but, at least for one of the two cases, major deficiencies are not offset by the use of Reanalysis data.