This project aims to examine the relationships between aerosol changes, cloud changes and climate change using the Integrated Massively Parallel Atmospheric Chemical Transport (IMPACT) aerosol model coupled to two different climate models and to evaluate the adequacy of the aerosol treatment and cloud treatments within the two versions of the coupled IMPACT/climate models. Specifically, the investigators will (i) couple the aerosol model to the Geophysical Fluid Dynamics Laboratory (GFDL) atmospheric general circulation model (AGCM) and the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM) models that will be used in the Intergovernmental Panel on Climate Change 5th assessment report (AR5) simulations, (ii) compare how different parameterizations in the models as well as basic model dynamics help determine the cloud fields, aerosol fields, and direct and indirect forcing by aerosols, and (iii) study the relative changes to clouds from changes in climate and from aerosols.
This project will help to determine which climate model transport, chemical transformation, and removal for aerosols is best able to reproduce satellite data for aerosol optical depth, ratio of extinction as a function of wavelength, backscattering profiles, and the effective radius of aerosols. It may also help to reduce the range of sensitivity of climate models to increases in greenhouse gases.
Broader impacts of this project concern both its policy implications and the training of scientific personnel. The issues being addressed are of prime importance in the determination of climate change and its prediction. The use of models that are being submitted to the next IPCC AR5 report will help the understanding and comparison two primary U.S. models used in that policy-relevant report. In addition, a graduate student as well as a post-doctoral will be trained and results from this project are routinely used to update the Precipitation and Clouds course taught by one of the investigators.
