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NARSTO Workshop on Innovative Methods for Emission Inventory Development and Evaluation University of Texas, Austin October 14-17, 2003 |
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Leaf, Canopy, Landscape, and Regional Measurements for Developing and Evaluating Biogenic VOC Emission Models
Alex Guenther, Jim Greenberg, Peter Harley, Thomas Karl,
Eiko Nemitz, Andrew Turnipseed, Christine Wiedinmyer
Biosphere-Atmosphere Interactions Group, Atmospheric Chemistry Division,
National Center for Atmospheric Research, Boulder, CO, USA
Biogenic volatile organic compounds (BVOC) have an important role in determining the chemical composition of atmosphere. As a result, these compounds may be important for air quality, visibility, biogeochemical cycling, climate and radiative forcing, and the health of the biosphere. This presentation will provide an overview of recent field measurements of biogenic VOC emissions from North American (Canada, U.S., Costa Rica) landscapes. Flux measurement methods that will be described include leaf-scale (enclosure measurements), canopy-scale (above-canopy tower measurements), landscape-scale (tethered balloon), and regional-scale (aircraft measurements) observations. Isoprene, methanol, á-pinene, â-pinene, acetaldehyde, acetone, ethanol, and ethene contribute more than 75% of the total North American BVOC carbon flux with an additional 25 BVOC contributing nearly all of the remainder. Recent advances in analytical techniques have considerably improved our ability to measure most of these compounds. These have been applied to enclosure measurement methods that have greatly increased our understanding of the physiological and genetic processes that control emission variations. Seasonal and diurnal variations characterized with above-canopy tower eddy flux measurements enable us to evaluate canopy scale emission models. Tethered balloon observations throughout the daytime mixed layer are used to examine the combined processes of emissions, transport and chemistry. Airborne studies are the most effective means of quantifying regional BVOC fluxes and recent advances, and plans for future work, will be described.