A flash-flood episode affecting a small area inApulia (south-eastern Italy) on 22 October 2005 is documented.A rainfall amount of 160mm was recorded in a 6 hinterval in the central part of the region, producing severedamage and causing six fatalities. Synoptic maps, observationsfrom surface stations and remote-sensing data are usedhere to describe the evolution of the rainfall system. Thevertical profiles show features similar to those observed inother orographic heavy-rain events, such as a low-level jet,a conditionally unstable environment, and a nearly saturatedwarm low-level air mass. The low hills in the centre of theregion play an important role in the release of the instabilityand the localisation of the rainfall, providing the upliftnecessary to the air parcels to reach the level of free convection.Numerical simulations are performed in order tounderstand the mechanisms responsible for the heavy rainevent. The Weather Research and Forecasting model (WRF)is setup in a 2-way nesting configuration including two domains.The model is able to realistically simulate the evolutionof the precipitation system and to capture fairly well thelocalisation, the amount and the timing of the rainfall. Thesimulations suggest the important synergy of low and uppertroposphericfeatures which act as the triggering mechanismfor the development of convection. A sensitivity experimentconfirms the importance of the orography for the developmentof convective cells.
An observational and numerical analysis of a flash-flood event over south-eastern Italy
Miglietta, M.;
2008
Abstract
A flash-flood episode affecting a small area inApulia (south-eastern Italy) on 22 October 2005 is documented.A rainfall amount of 160mm was recorded in a 6 hinterval in the central part of the region, producing severedamage and causing six fatalities. Synoptic maps, observationsfrom surface stations and remote-sensing data are usedhere to describe the evolution of the rainfall system. Thevertical profiles show features similar to those observed inother orographic heavy-rain events, such as a low-level jet,a conditionally unstable environment, and a nearly saturatedwarm low-level air mass. The low hills in the centre of theregion play an important role in the release of the instabilityand the localisation of the rainfall, providing the upliftnecessary to the air parcels to reach the level of free convection.Numerical simulations are performed in order tounderstand the mechanisms responsible for the heavy rainevent. The Weather Research and Forecasting model (WRF)is setup in a 2-way nesting configuration including two domains.The model is able to realistically simulate the evolutionof the precipitation system and to capture fairly well thelocalisation, the amount and the timing of the rainfall. Thesimulations suggest the important synergy of low and uppertroposphericfeatures which act as the triggering mechanismfor the development of convection. A sensitivity experimentconfirms the importance of the orography for the developmentof convective cells.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
