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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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Global Inventory of Nitrogen Oxide Emissions Constrained By Space-based Observations of NO2 Columns
R.V. Martin 1,2, D.J. Jacob 3, K.V. Chance 2, T.P. Kurosu 2, P.I. Palmer 3, M.J. Evans 3
1 Dalhousie University
2 Harvard-Smithsonian Center for Astrophysics
3 Division of Engineering and Applied Sciences, Harvard University
We use tropospheric NO2 columns that we retrieve from the Global Ozone Monitoring Experiment (GOME) satellite instrument for 1996-97 to derive top-down constraints on emissions of nitrogen oxides (NOx = NO + NO2), and combine these with a priori information from a bottom-up emission inventory (with error weighting) to achieve an optimized a posteriori estimate of the global distribution of NOx emissions. The a priori inventory is based on the Global Emission Inventory Activity and scaled to 1996-97. We use the GEOS-CHEM model to calculate the local relationship between GOME NO2 columns and NOx emissions as our top-down constraint. The derived NOx emissions for industrial regions are aseasonal, despite large seasonal variations in NO2 columns, confirming the validity of the method. Top-down errors in monthly NOx emissions are about 50%, comparable to bottom-up errors over source regions. Our global a posteriori estimate for annual land surface NOx emissions (37.7 Tg N yr-1) agrees closely with the a priori (36.4) and with an independent bottom-up inventory (EDGAR 3.0) (36.6). Spatial and monthly variations in a posteriori emissions are similar to the a priori (r2=0.86), but there are significant regional differences. A posteriori NOx emissions are higher by 50-100% in the Po Valley, Tehran, and Riyadh urban areas, and by 25-35% in Japan and South Africa. Biomass burning emissions from India, central Africa, and Brazil are lower by up to 50%; soil NOx emissions are appreciably higher in the western United States, the Sahel, and southern Europe.