A Climatology of the Mesoscale Environment Associated with Heavily Precipitating Events over a Northwestern Mediterranean Area
Open Access
- 1 March 2012
- journal article
- Published by American Meteorological Society in Journal of Applied Meteorology and Climatology
- Vol. 51 (3), 468-488
- https://doi.org/10.1175/jamc-d-11-017.1
Abstract
A climatological approach is developed to characterize the mesoscale environment in which heavily precipitating events (HPEs) grow over a mountainous Mediterranean area. This climatology that is based on three-dimensional variational data assimilation (3D-Var) mesoscale analyses is performed for a 5-yr period, considering cases with daily precipitation of >150 mm occurring over southern France during autumn. Different diagnostics are used to document the time evolution of mesoscale features associated with the HPEs for initiation, mature, and dissipation stages. To underline differences according to the location of precipitation, four subdomains are also considered: Languedoc-Roussillon, Cévennes-Vivarais, South Alps, and Corsica. Composite analyses show that these events are driven by some common features (slowly evolving trough–ridge pattern and diffluent midlevel flow). Instability and moisture are transported by the low-level jet (LLJ) toward the target area from their sources, which are located upstream over the Mediterranean Sea. Strong moisture convergence is located within the left exit of the LLJ. These parameters reach a maximum during the mature stage. During the life cycle of the HPEs, the low-level winds rotate clockwise. Composite analyses also show that the synoptic and mesoscale patterns can differ greatly as a function of the location of the precipitation. Indeed, the LLJ varies from southeasterly to southwesterly. The midlevel flow varies from southerly to southwesterly. The areas of high moisture and instability are stretched in different orientations. Long-lasting events are associated with a more pronounced quasi-stationary trough–ridge pattern, higher values of CAPE, a wetter troposphere, and faster LLJ. The most-heavily precipitating events are found to be in general associated with higher values of these parameters or with a low-level inflow that is closer to perpendicular to the relief.Keywords
This publication has 34 references indexed in Scilit:
- Idealized mesoscale numerical study of Mediterranean heavy precipitating convective systemsArchiv für Meteorologie, Geophysik und Bioklimatologie Serie A, 2009
- Impact of initial condition uncertainties on the predictability of heavy rainfall in the Mediterranean: a case studyQuarterly Journal of the Royal Meteorological Society, 2008
- A numerical study of three catastrophic precipitating events over southern France. II: Mesoscale triggering and stationarity factorsQuarterly Journal of the Royal Meteorological Society, 2008
- The Use of Moisture Flux Convergence in Forecasting Convective Initiation: Historical and Operational PerspectivesWeather and Forecasting, 2005
- The Catastrophic Flash-Flood Event of 8–9 September 2002 in the Gard Region, France: A First Case Study for the Cévennes–Vivarais Mediterranean Hydrometeorological ObservatoryJournal of Hydrometeorology, 2005
- Storm-Scale Numerical Rainfall Prediction for Five Precipitating Events over France: On the Importance of the Initial Humidity FieldWeather and Forecasting, 2002
- The MAP Special Observing PeriodBulletin of the American Meteorological Society, 2001
- Mesoscale analyses and diagnostic parameters for deep convection nowcastingMeteorlogical Applications, 2000
- Numerical Simulations of the 1994 Piedmont Flood: Role of Orography and Moist ProcessesMonthly Weather Review, 1998
- Flash Flood Forecasting: An Ingredients-Based MethodologyWeather and Forecasting, 1996