Research Highlights
September 2007
Keeping Aerosol Research on the Straight and Narrow
Strategy Paper Describes Complex Path from Field Measurements to Climate Models
In a defining document about the future of aerosol research, Pacific Northwest National Laboratory scientist Steve Ghan teamed with Brookhaven National Laboratory's Steve Schwartz, Chief Scientist for the Department of Energy's Atmospheric Science Program, to describe a disciplined process for successfully moving aerosol research from the observational stage to model simulations. Published in the Bulletin of the American Meteorological Society in July, the paper discusses the challenges faced by both the measurement and modeling communities, ways to overcome them, and the resulting benefits.
"Other strategy papers related to global aerosol modeling have been published over the years, but this one focuses on how different research programs can work together to address the breadth of challenges inherent in such a complex system," said Ghan.
Aerosols are one of the greatest sources of uncertainty in climate science. Much of this uncertainty is due to the complexity of aerosols and their interactions with and impacts on cloud processes and properties, as well as the wide range of scales on which these interactions occur. Accurate representation within global climate models of aerosol properties and the processes that influence those properties is a significant challenge facing the scientific community.
"Until recently, aerosol processes were under-represented in global climate models because of disconnects between various research programs," explained Ghan. "This paper describes a framework for coordinating aerosol research across DOE's climate research programs, which will ensure that progress in aerosol research is accurately reflected in future generations of climate models."
The role of aerosols in climate is a key factor in assessment and prediction of climate changes, as well as in advancing climate modeling frameworks. Enlarge image
In their paper, Ghan and Schwartz outline a strategy for incorporating aerosol measurements into modeling frameworks within DOE's research programs to improve descriptions and parameterizations of potential impacts of aerosols on the changing climate. Similar to the model development process adopted for other components of the climate system, this strategy is composed of four stages, each one building on the next.
Field and laboratory studies provide the foundation for Stage 1, which focuses on improving scientific understanding of isolated atmospheric processes. Stage 2 uses these measurements to develop and evaluate models that represent these individual aerosol and cloud processes and properties. These models focus on small numbers of aerosol properties or processes.
During Stage 3, these process and property models are incorporated into integrated aerosol models at the regional scale and then at the global scale. Regional aerosol models represent important aerosol properties and processes by integrating a suite of property and process models for a limited geographic area over a limited time span. Global aerosol models are similar to regional aerosol models, but with a coarser resolution, a broader geographic area, and a longer time span. In Stage 4, these aerosol models are validated and coupled to global climate models, which also incorporate models of the land surface, ocean, and sea ice.
Global climate models are essential tools for understanding climate change and for developing policy regarding future emissions of greenhouse gases, primary aerosol particles, and aerosol precursor gases. With support from several programs within DOE's Climate Change Research Division, this strategy promises substantial advances in understanding and quantifying aerosol-related atmospheric phenomena throughout the next several generations of climate models.
Acknowledgments: This work was funded by the DOE Office of Science, Office of Biological and Environmental Research.
Reference: Ghan, S.J., and S.E. Schwartz, 2007: Aerosol Properties and Processes: A Path from Field and Laboratory Measurements to Global Climate Models. Bull. Amer. Meteor. Soc., 88, 1059-1083.