AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Aerosol Precursor Concentrations and Fluxes from a Temperate Deciduous Forest in East Tennessee
RICK SAYLOR, Ariel Stein, NOAA Air Resources Laboratory
Abstract Number: 43 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Forests are a dominant source of biogenic volatile organic compound (BVOC) emissions into the earth’s atmosphere and thus play an important role in the formation of secondary organic aerosol (SOA). To arrive at a better scientific understanding of the complex chemical and physical processes of forest-atmosphere exchange and provide a platform for robust analysis of field measurements of these processes, a process-level, multiphase model of the atmospheric chemistry and physics of forest canopies is being developed. The initial gas-phase version of the model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS) currently includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer, detailed chemical reactions, mixing with the background atmosphere and bi-directional exchange between the atmosphere and the canopy and the forest floor.
The Walker Branch Watershed (WBW) is a dedicated ecosystem research area on the U. S. Department of Energy’s Oak Ridge Reservation in east Tennessee. A flux tower located within the watershed (35°57´30˝N, 84°17´15˝W; 365 m above mean sea level) and 10 km southwest of Oak Ridge, Tennessee, served as a focal point for BVOC chemical flux measurements from the forest canopy in 1999. At the time of the measurements, the forest stand was approximately 50 years old, the overstory canopy height was 26 m, and the whole canopy leaf area index was 6.0 m$^2 leaf/m$^2 ground area. In this presentation, the ACCESS model will be briefly described and results from its application to the WBW forest canopy will be presented and compared to measurements made at the site. Levels of background NO$_x concentrations are found to significantly influence both the magnitude and chemical composition of fluxes of SOA precursors from the canopy.