Multi-scale Modeling of Cloud-Aerosol Interactions

To represent cloud-aerosol interactions at scales from the microscale of droplet formation, the turbulence scale of boundary layer clouds, the plume scale of deep convection, and the global scale of the atmospheric circulation, we have integrated the Cloud Layers Unified By Binormals (CLUBB) turbulence scheme into the SP-CAM multi-scale modeling framework, in which a two-dimensional cloud-resolving model with double-moment cloud microphysics is embedded within each grid cell of the Community Atmosphere Model and used to drive a physically-based parameterization of cloud effects on the aerosol. CLUBB significantly improves the simulation of boundary layer clouds. In the presentation we will compare estimates of effective radiative forcing by aerosol-cloud interactions (ERFaci) using SP-CAM-CLUBB with estimates by SP-CAM without CLUBB and by CAM5, and diagnose explanations for the differences between the estimates.