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Atmospheric Composition

The proposed research will advance scientific understanding of the emissions and atmospheric chemistry of isoprene and methanol, the two most important biogenic volatile organic compounds (VOCs). The work involves 3D chemical transport model simulations (GEOS-Chem CTM) and analysis of satellite (TES: methanol; OMI: formaldehyde and glyoxal) and in-situ observations. Research will be guided by the following overarching questions: 1) What is the distribution of biogenic VOC (BVOC) fluxes to the global atmosphere? 2) How do emissions vary with season and environmental forcing? 3) What is the resulting seasonal impact on tropospheric chemistry via photochemical production of key carbonyls and CO?

Atmospheric VOCs play a critical role in tropospheric chemistry as precursors of tropospheric ozone, carbon monoxide, formaldehyde, and secondary organic aerosol.
The global biosphere is the dominant source of VOCs to the atmosphere, with emissions of isoprene and methanol each estimated to be greater than those of all anthropogenic VOCs combined. These compounds raise several fundamental issues to be resolved: (i) bottom-up BVOC inventories are mainly based on extrapolation of localized measurements and are highly uncertain; (ii) we lack the data to constrain BVOC fluxes over large parts of the globe, and to quantify how emissions depend on environmental drivers and on season; and (iii) the impact of BVOCs on tropospheric composition is poorly known due to uncertainties in the emission fluxes and in their NOx-dependent photochemistry.

This project will significantly advance the resolution of these key issues. Specific activities will include: A) Analysis of TES methanol retrievals over targeted regions to improve process understanding of seasonal methanol emissions from plant functional types. We will use GEOS-Chem to interpret the TES data in combination with aircraft measurements to develop a consistent set of constraints on emission fluxes.
B) Apply GEOS-Chem to interpret the full TES dataset over one year in terms of implications for the global methanol budget and the role of methanol as a source of formaldehyde and CO. C) Use formaldehyde column measurements from OMI to develop a new understanding of global isoprene emissions. This work will combine recent advances in mechanistic understanding of isoprene chemistry with the new TES-derived constraints on global methanol sources (Tasks A-B) for a more accurate diagnosis of the isoprene- formaldehyde relationship. D) Combine the new information on isoprene and methanol emissions (Tasks A-C) with glyoxal column measurements from OMI to test current understanding of BVOC photooxidation and production of key atmospheric carbonyls and CO.

The work directly addresses the core aims of this solicitation related to "tropospheric air quality and oxidation efficiency" and "the emission, transport, and oxidation of hydrocarbons".

Project PI: Dylan Millet/University of Minnesota

Borlaug Hall 1991 Upper Buford Circle St. Paul, MN 55108

Phone: (612)626-3259

Fax: (612)626-3259

Email: dbm@umn.edu

http://www.atmoschem.umn.edu/

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Started: Sep 03, 2010

Last Activity: Feb 02, 2011

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