We examine the major outflow pathways for North American pollution to the Atlantic in summer by conducting a 4-year simulation with the GEOS-CHEM global chemical transport model, including a coupled ozone-aerosol simulation with 1° Â 1° horizontal resolution for summer 2000. The outflow is driven principally by cyclones tracking eastward across North America at 45–55°N, every 5 days on average. Anthropogenic and fire effluents from western North America are mostly transported north and east, eventually merging with the eastern U.S. pollution outflow to the Atlantic. A semipermanent upper-level anticyclone traps the convective outflow and allows it to age in the upper troposphere over the United States for several days. Rapid ozone production takes place in this outflow, driven in part by anthropogenic and lightning NOx and in part by HOx radicals produced from convectively lifted CH2O that originates from biogenic isoprene. This mechanism could explain ozonesonde observations of elevated ozone in the upper troposphere over the southeastern United States. Asian and European pollution influences in the North American outflow to the Atlantic are found to be dispersed into the background and do not generate distinct plumes. Satellite observations of CO columns from MOPITT and of aerosol optical depths (AODs) from MODIS provide useful mapping of outflow events, despite their restriction to clear-sky scenes.
North American pollution outflow and the trapping of convectively lifted pollution by upper-level anticyclone
Li, Q., D.J. Jacob, R. Park, Y. Wang, C.L. Heald, . Hudman, R. Yantosca, and R. Martin (2005), North American pollution outflow and the trapping of convectively lifted pollution by upper-level anticyclone, J. Geophys. Res., 110, D10301, doi:10.1029/2004JD005039.
Abstract
PDF of Publication
Download from publisher's website
Research Program
Atmospheric Composition Modeling and Analysis Program (ACMAP)
Tropospheric Composition Program (TCP)
Mission
INTEX-NA
Disclaimer: This material is being kept online for historical purposes. Though accurate at the time of publication, it is no longer being updated. The page may contain broken links or outdated information, and parts may not function in current web browsers. Visit https://espo.nasa.gov for information about our current projects.