Colloquium: Dr. Thijs Heus, Cleveland State University

ABSTRACT: Low-level cumulus clouds are one of the largest uncertainties in weather and climate prediction. This is in part because of several feedback processes, where changes in the Earth radiative budget alter the cloud structure, which in turns alters the radiation. The issue is further exacerbated by the cloud size: Cumulus clouds have a typical size of up to a few km, while typical climate models have a much coarser resolution than that, and weather forecasting models have a resolution on the order of the largest clouds. To develop parameterizations for cumulus convection, we need to know what 1) What the cloud size distribution is, and how to properly retrieve it from observations, 2) Understand how the effective area of clouds increases albedo (cloud overlap), and 3) Understand how cloud clustering and organization may affect the radiative properties of the clouds. In order to do so, I will present results from high-resolution Large Eddy Simulations, that can resolve these cloud fields up to high accuracy.