Développement d'un modèle de nuage tridimensionnel à microphysique détaillée - Application à la simulation de cas de convection profonde

摘要

Clouds are a great source of uncertainties in synoptic models and GCM (Global Climate Models). To improve the treatment of clouds in those models, a high resolved 3D cloud model with detailed (bin) microphysics has been developed at the Laboratoire de Météorologie Physique. A comparison with bulk microphysical models will allow their calibration. The first model for warm clouds (Leporini, 2005) couples the dynamics of the NCAR Clark-Hall cloud scale model (Clark and Hall, 1991) with the DEtailed SCAvenging Model (DESCAM) of Flossmann et al. (1985). This thesis focuses on the implementation of an ice phase module. The updated microphysical scheme follows the evolution of aerosol particle, drop and ice crystal spectra each with 39 bins. Aerosol mass in drops and ice crystals is predicted by two distribution functions in order to close the aerosol budget. This detailed model called DESCAM-3D is thus a very efficient tool to study the aerosol-clouds interactions.To validate DESCAM-3D, we compared the model results with airborne observations inside a cumulonimbus from CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment) and with ground based measurements of precipitation during a medium convective case over the Cévennes' foothills. Sensitivity studies were also made concerning the total number of aerosol particles. The number of aerosol particles in the boundary layer is found to influence precipitation but also the dynamic evolution of the cloud and consequently can have impacts on the properties of the anvil of convective clouds.