Abstract
Abstract. This study is embedded into a wider project named "Tackle deficiencies in Quantitative Precipitation Forecast (QPF)'' in the framework of the COSMO (COnsortium for Small-scale MOdelling) community. In fact QPF is an important purpose of a numerical weather prediction model, for forecasters and customers. Unfortunately, precipitation is also a very difficult parameter to forecast quantitatively. This priority project aims at looking into the COSMO Model deficiencies concerning QPF by running different numerical simulations of various events not correctly predicted by the model. In particular, this work refers to a severe event (moist convection) happened in Piemonte region during summer 2006. On one side the results suggest that details in orography representation have a strong influence on accuracy of QPF. On the other side COSMO Model exhibits a poor sensitivity on changes in numerical and physical settings when measured in terms of QPF improvements. The conclusions, although not too general, give some hint towards the behaviour of the COSMO Model in a typical convective situation.
Highlights
The main goal of this project was to gain a deeper understanding of the COSMO Model problems in terms of Quantitative Precipitation Forecast (QPF)
Milelli cross experiments performed in a second step on which we focus in this work
Concerning the Piemonte event, the results vary according to the area of averaging but in general, the QPF of COSMO Model at 7 km shows a certain insensitivity with respect to change in its physical and numerical formulation
Summary
The test case here described considers a severe rainfall event, which affected the Northern part of Piemonte, at the border with Switzerland, during 17–18 August 2006. The event was mainly convective in nature and characterized by the occurrence of intense deep moist convection leading to relevant rainfall depths. The results of the numerical experiments are compared in terms of peak and mean rainfall depths over the catchments both for short duration (6 h, not shown here, see Milelli et al, 2007) and long duration (24 h). The analysis of the results helps in giving a more precise idea about the model parameters, about what parts of the model need to be reformulated in order to improve the QPF and about the scales which can be solved by the model. This work will focus on some of the most relevant simulations
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