Ammonia emissions in the United States, European Union, and China derived by high-resolution inversion of ammonium wet deposition data: Interpretation with a new agricultural emissions inventory (MASAGE_NH3)

• Published in: Journal of geophysical research. Atmospheres 2014-04, Vol.119 (7), p.4343-4364
• Main Authors: Paulot, F., Jacob, D. J., Pinder, R. W., Bash, J. O., Travis, K., Henze, D. K.
• Format: Article
• Language: English
• Subjects: Adjoints; agriculture; Ammonia; Ammonium; Chemical transport; China; Deposition; Double cropping; Emission inventories; emission inventory; European union; Fertilizer application; Fertilizing; Geophysics; Inventories; inverse method; Inversions; Livestock; Mineral fertilizers; Seasonal variations; Spring; Stockpiling; Summer; Wet deposition
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2013JD021130

We use the adjoint of a global 3‐D chemical transport model (GEOS‐Chem) to optimize ammonia (NH3) emissions in the U.S., European Union, and China by inversion of 2005–2008 network data for NH4+ wet deposition fluxes. Optimized emissions are derived on a 2° × 2.5° grid for individual months and years. Error characterization in the optimization includes model errors in precipitation. Annual optimized emissions are 2.8 Tg NH3−N a−1 for the contiguous U.S., 3.1 Tg NH3−N a−1 for the European Union, and 8.4 Tg NH3−N a−1 for China. Comparisons to previous inventories for the U.S. and European Union show consistency (∼±15%) in annual totals but some large spatial and seasonal differences. We develop a new global bottom‐up inventory of NH3 emissions (Magnitude And Seasonality of Agricultural Emissions model for NH3 (MASAGE_NH3)) to interpret the results of the adjoint optimization. MASAGE_NH3 provides information on the magnitude and seasonality of NH3 emissions from individual crop and livestock sources on a 0.5° × 0.5° grid. We find that U.S. emissions peak in the spring in the Midwest due to corn fertilization and in the summer elsewhere due to manure. The seasonality of European emissions is more homogeneous with a well‐defined maximum in spring associated with manure and mineral fertilizer application. There is some evidence for the effect of European regulations of NH3 emissions, notably a large fall decrease in northern Europe. Emissions in China peak in summer because of the summertime application of fertilizer for double cropping. Key Points Adjoint‐based inversion of ammonium wet deposition in the U.S., Europe, and ChinaMuch larger spatial and temporal variability of U.S. emission than in the a prioriNew model of NH3 emissions reproduces the patterns of the optimized emissions