Didier Ricard is an atmospheric physicist and meteorological researcher affiliated with the Centre National de Recherche Météorogique (CNRM, part of Météo-France). He holds a PhD in atmospheric physics from the University of Toulouse (2002) and is a specialist in modeling intense meteorological phenomena using Cloud Resolving Models or Large Eddy Simulations. He has worked in particular on mesoscale data assimilation and the forecasting of intense rainfall in the Mediterranean region. He has also studied the impact of resolution and diabatic processes on the modeling of extratropical storms. He is interested in the interaction between deep convection and turbulence. Since 2020, he has been leading a team working on improving physical parameterizations for kilometer-scale and hectometer-scale meteorological models, the Meso-NH research model and the AROME forecasting model used at Météo-France. He contributes to improving the turbulence scheme of these models.
Mesoscale Environment of Heavily Precipitating Mediterranean Systems and Numerical Simulations of Severe Mediterranean Convection Events
The western Mediterranean mountainous areas are prone to heavily precipitating events (HPE) during the fall season. A climatological approach, based on mesoscale analyses, is developed to characterize the mesoscale environment in which HPEs grow over a mountainous Mediterranean area, during their initiation, mature, and dissipation stages. 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. The most-heavily precipitating events are found to be in general associated with higher values of these parameters or with a LLJ that is closer to perpendicular to the relief.
Thus, the ingredients that favour these HPEs are well known but it is still difficult to understand why a precipitating system can become paroxysmal or to forecast the accurate location of the system. To investigate these predictability issues, an idealized framework to simulate quasi-stationary mesoscale convective systems (MCS) with the Meso-NH model is set up and serves as a basis for studying the sensitivity of the location and intensity of precipitating systems to the characteristics of the low-level upstream flow over the Mediterranean Sea. Low-level humidity distribution, convective available potential energy and speed of the flow are varied. It is found that various lifting mechanisms are involved to explain the specific location (orographic lifting, cold pool dynamics, low-level convergence due to deflection of the flow by mountains).
We have also simulated a real case of a Mediterranean MCS: the derecho of the 18 August 2022 that hit Corsica with an unprecedented violence. Sensitivity study to physical parameterisations (turbulence, microphysics) and resolution (1km, 250 m) will be presented.