Aerosols play several important roles in the atmosphere. They are important components of biogeochemical cycles and participate in heterogeneous chemistry that affects trace gases in the troposphere and the stratosphere. They are known to play important roles in visibility reduction and climate change. Significant progress has been made in characterizing the atmospheric aerosol, in elucidating its sources, transformations, and sinks, and in understanding its interaction with radiation; long-term monitoring is yielding useful information on trends and on the global distribution of particulate matter. Significant future research challenges include the simultaneous characterization of aerosol physical, chemical and optical properties relevant to climate change and remote sensing applications; theoretical and observational studies of particle microphysical behavior, including nucleation phenomena; development of improved descriptions of the nature and roles of carbonaceous aerosols; and development of interactive global models of aerosol evolution and transport.
Acknowledgments. This material is based upon work supported in part by the National Science Foundation under Grant No. ATM-9215951.