HR: 16:20h
AN: A44B-02 INVITED     [Abstracts]
TI: Soil Emissions of Nitrogen Oxides: Constraints From Satellite Observations
AU: * Jaeglé, L
EM: jaegle@atmos.washington.edu
AF: Department of Atmospheric Sciences, University of Washington, BOX 351640, Seattle, WA 98195 United States
AU: Martin, R
EM: rvmartin@fizz.phys.dal.ca
AF: Department of Physics and Atmospheric Science, Dalhousie University, Halifax, B3H 3J5 Canada
AU: Chance, K
EM: kchance@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 United States
AB: We use space-based observations of NO₂ columns from the Global Ozone Monitoring Experiment (GOME) to derive monthly top-down NO_x emissions for 2000 via inverse modeling with the GEOS-CHEM chemical transport model. Top-down NO_x sources are partitioned among fuel combustion, biomass burning and soils by exploiting the spatio-temporal distribution of remotely sensed fires and a priori information on the location of regions dominated by fuel combustion. The top-down inventory is combined with an a priori inventory to obtain an optimized a posteriori estimate. A posteriori fuel combustion, biomass burning and soil emissions account for 64% (25.6 TgN/yr), 14% (5.8 TgN/yr), and 22% (8.9 TgN/yr) of global surface NO_x emissions, respectively. The annual a posteriori fuel combustion and biomass burning inventories agree closely with the a priori, and errors are significantly reduced. A posteriori estimates of soil emissions are 68% larger than a priori (5.3 TgN/yr). The a posteriori inventory displays the largest soil emissions over tropical savanna/woodland ecosystems (Africa), as well as over agricultural regions in the western U.S. (Great Plains), southern Europe (Spain, Greece, Turkey), and Asia (North China Plain and North India), consistent with field measurements. Emissions over these regions are highest during summer at mid-latitudes and during the rainy season in the Tropics. We infer a significant role for soil NO_x emissions at northern mid-latitudes during summer, where they account for nearly half that of the fuel combustion source, a doubling relative to the a priori. We increase soil emissions in the GEOS-CHEM model to match our inferred a posteriori soil emissions and we examine the implications of these large soil emissions on background ozone levels and HNO₃ deposition. We assess the consistency of our results with observations of ozone and HNO₃ deposition in rural areas over the United States (Clean Air Status and Trends Network) and elsewhere.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005