Title : Turbulence, Clouds and Climate: the Subtropical Cloud Transition

Abstract: The Intergovernmental Panel on Climate Change (IPCC) has reiterated that clouds remain the largest source of uncertainty in climate projections. Clouds in the atmospheric boundary layer, and in particular the subtropical cloud transition from stratocumulus to cumulus, appear to play a key role in cloud-climate feedbacks. Recent studies have highlighted the lack of complete understanding of this transition and the fact that climate models do not simulate in a realistic manner the physics of the transition.

In this presentation, recent results on the global characterization of the subtropical cloud transition are used to illustrate its essential properties and the key questions remaining for a complete understanding of the transition. A new approach (EDMF) - which combines eddy-diffusivity (ED) methods that represent small-scale turbulence with mass-flux (MF) methods that represent moist convective plume dynamics - is proposed to represent in a unified manner the turbulent and convective properties of the transition. Large-Eddy Simulations (LES) of the cloud transition are used to develop simple models of the transition and a better understanding of the small-scale dynamics that leads to the ultimate demise of stratocumulus.

Speaker's website: http://science.jpl.nasa.gov/people/Teixeira/