Articles | Volume 12, issue 8
Nat. Hazards Earth Syst. Sci., 12, 2631–2645, 2012

Special issue: Forecast and projection in climate scenario of Mediterranean...

Nat. Hazards Earth Syst. Sci., 12, 2631–2645, 2012

Research article 21 Aug 2012

Research article | 21 Aug 2012

Hydro-meteorological evaluation of a convection-permitting ensemble prediction system for Mediterranean heavy precipitating events

B. Vié1, G. Molinié2, O. Nuissier1, B. Vincendon1, V. Ducrocq1, F. Bouttier1, and E. Richard3 B. Vié et al.
  • 1Groupe d'étude de l'atmosphère météorologique (GAME) – URA1357, Météo-France/CNRS, Toulouse, France
  • 2LTHE, Laboratoire d'études des transferts en hydrologie et environnement – (CNRS, UJF, IRD, INPG), Grenoble, France
  • 3Laboratoire d'Aérologie, CNRS et Université de Toulouse, Toulouse, France

Abstract. An assessment of the performance of different convection-permitting ensemble prediction systems (EPSs) is performed, with a focus on Heavy Precipitating Events (HPEs). The convective-scale EPS configuration includes perturbations of lateral boundary conditions (LBCs) by using a global ensemble to provide LBCs, initial conditions (ICs) through an ensemble data assimilation technique and perturbations of microphysical parameterisations to account for part of model errors. A probabilistic evaluation is conducted over an 18-day period. A clear improvement is found when uncertainties on LBCs and ICs are considered together, but the chosen microphysical perturbations have no significant impact on probabilistic scores.

Innovative evaluation processes for three HPE case studies are implemented. First, maxima diagrams provide a multi-scale analysis of intense rainfall. Second, an hydrological evaluation is performed through the computation of discharge forecasts using hourly ensemble precipitation forecasts as an input. All ensembles behave similarly, but differences are found highlighting the impact of microphysical perturbations on HPEs forecasts, especially for cases involving complex small-scale processes.