Radiative transfer in heterogeneous boundary layer clouds

Heterogeneity in boundary layer clouds is the sum of the 3D variability of cloudy water and the 3D microphysical variability (i.e. local dimensional distributions and concentration of cloud droplets). In this study, the radiative impact of this heterogeneity is explored on both the albedo computation of a mesh within a low resolution model (GCM), and on the cloud parameters retrieval from satellites.<br />The developed method employs together LES simulations, two extreme entrainment/mixing schemes and a 3D radiative transfer model. The simulated fields are constrained by comparison with in-situ and remote sensing measurements.<br />It is shown that the microphysical variability is the major source of uncertainty in both albedo computations within GCM and cloud microphysical parameters retrieval. This can lead to a significant overestimation of the first aerosol indirect effect by GCMs and a significant underestimation of its measurement using satellite remote sensing.