On the performance of a limited area model for quantitative precipitation forecast over Calabria

At Crati Scrl an operational version of RAMS 4.3 (Regional Atmospheric Modeling System), with a son grid over Calabria, was implemented in January 2001. This paper aims to give a first assessment of model performances for quantitative precipitation forecast (QPF). In particular two issues of weather forecast are discussed. First problem refers to effects introduced by enhanced resolution over Calabria, using a 6 km resolution grid nested in a 30 km parent grid. Second issue discusses forecast deterioration with increasing forecast time. To cope with these problems, two sets of integrations are discussed using two different model configurations. Differences between configurations are only due to model resolutions. Integrations are performed daily for six months. Each integration starts at 12 UTC and lasts for 60 h, with 12 h spin-up time. ECMWF 12 UTC analysis and following forecast are used as initial and dynamic boundary conditions. Models performances are evaluated computing scores by comparing model outputs with raingauges data coming from Calabria regional network. Results show better performances of finer-grid resolution compared to the coarser one and confirms the usefulness of enhanced resolution over complex terrain. In addition, performances decrease with increasing forecast time with first integration day performing better than second forecast day but differences are not statistically significant at 5% level.