The Impacts of Model Representation of Aerosol-Cloud Interaction on the Radiative Forcing and Climate Response of Anthropogenic Aerosols (Invited Presentation)

The climate response to anthropogenic aerosols is a critical while not fully understood aspect in climate science. The recent Coupled Model Intercomparison Project Phase 5 has included, for the first time, a sizable group of models equipped with physically based parameterizations of cloud and aerosol processes and thus aerosol-cloud interaction to perform long historical transient climate simulations. Our analysis has indicated that these models are able to produce changing patterns of both surface temperature and precipitation in the past that are much closer to the reanalysis data in comparison to the models with more simplified representations of aerosol-cloud interaction. Aerosol-cloud interaction initiates from the nucleation of both liquid and ice particles. Using different liquid droplet nucleation schemes including our own that was developed by applying detailed parcel model and polynomial chaos expansion method, we have identified a clear difference in modeled radiative effects of anthropogenic aerosols. Such a discrepancy leads to modeled climate responses differing in magnitude and spatial distribution. In addition, we have found that different methods to correct the known instrumental bias in measuring ice nucleation particles can substantially affect the ice nucleation parameterization and thus modeled radiative effects of aerosols.