Abstract : H.4
Sensitivity study on assimilation of non-GTS data and soil moisture initialization

Antonella Sanna, Daniele Cane, Davide Rabuffetti, Massimo Milelli
ARPA- Piemonte

This study is worked out in the framework of the PREVIEW (PREVention, Information and Early Warning) project, part of the EU Sixth Framework Program and, in particular, inside the WP4340 (Very Short Range Flash-Flood Laboratory), with the purpose of improving the very short-range forecast of Mediterranean flash floods over medium-sized basins, on the base of the next generation of European high-resolution NWP models.

Flash floods are one of the most common natural hazards in the Western Mediterranean region, where, during recent years, all the countries had to face with intense episodes and their consequences. This kind of phenomena is triggered by an intense rainfall over small catchments and the main cost is in terms of human lives, because its rapidity does not permit the actuation of alert procedures. For these reasons the forecasting of flash floods requires dedicated tools to cope with these smaller time and spatial scales. Piemonte is one of the pilot regions where flash-flood test cases have been selected (4-6 June 2002 and 1-2 September 2002) and where the impact of non-GTS data assimilation and soil moisture initialisation in high-resolution models will be studied. The hydrological model is a high resolution, distributed, complete model mainly designed for flood simulations. Water and energy budget are calculated at local scale with a simplified physical approach that allows solving an effective analytical numerical scheme. Soil parameterisation comes from regional soil and land use maps with a 1 km resolution. Effects of elevation, slope inclination and aspects on the interpolation of temperature and solar radiation influx fields are carefully accounted for. The meteorological model is the COSMO model Italian version developed inside the COnsortium for Small-scale MOdelling framework, an over-national consortium coordinates the cooperation of the national and regional weather services of Germany, Italy, Switzerland, Greece and Poland(www.cosmo-model.org)