Testing a Sectional Warm Cloud Microphysics Scheme

Warm clouds have significant radiative effects on the climate system. Nonetheless, currently in GCMs, the simulated mid- and low-level clouds cause the leading inter-model discrepancies in cloud feedbacks and climate sensitivity [Bony & Dufresne, 2005; Webb et al., 2006; IPCC, 2013]. In order to better simulate the global warm cloud field, we try to couple a sectional warm cloud scheme to the NFS/DOE/NCAR/CESM model. Warm cloud microphysical processes (e.g. falling, coagulation/coalescence) were first tested on a stand-alone 1-d sectional model based on the Community Aerosol and Radiation Model for Atmospheres (CARMA, v3.0). Model’s sensitivity to bin width and time step size were evaluated against analytical solutions.