Guest seminar: Brandon Duran, Scripps Institution of Oceanography, University of California San Diego

Abstract:
Efforts to constrain estimates of the effective radiative forcing (ERF) from aerosol–cloud interactions (ERFaci) have primarily focused on aerosol effects on liquid clouds. In contrast, the impact of aerosol effects on ice clouds is much less understood. Using a perturbed parameter ensemble (PPE) of CAM6 simulations, I investigate the response of ice clouds to anthropogenic aerosols and its sensitivity to key aerosol and microphysics parameters. I quantify the radiative impacts of changes in ice crystal size, ice water path, and ice cloud fraction using a new cloud radiative kernel framework. A pathway is proposed that relates aerosol-induced subtropical low cloud changes to tropical ice cloud changes via changes in boundary layer moisture. The PPE results demonstrate that dynamical changes can drive the SW aerosol forcing on ice clouds in certain regions, adding another dimension of complexity to aerosol–cloud interactions. Hence the simplistic picture of weak aerosol impacts on ice clouds is revealed to obscure substantial variability in aerosol–ice–cloud interactions, with potential implications for efforts to constrain ERFaci.

Bio: Brandon is a fifth-year PhD candidate at Scripps Institution of Oceanography, advised by Nicholas Lutsko and Shang-Ping Xie. His work is focused on developing new tools to quantify the components of aerosol-cloud interactions in global climate models, aimed at reducing uncertainty in estimates of aerosol forcing.