Regional sources of nitrous oxide over the United States: Seasonal variation and spatial distribution

Abstract

his paper presents top-down constraints on the magnitude, spatial distribution, andseasonality of nitrous oxide (N2O) emissions over the central United States. We analyzedata from tall towers in 2004 and 2008 using a high resolution Lagrangian particledispersion model paired with both geostatistical and Bayesian inversions. Our resultsindicate peak N2O emissions in June with a strong seasonal cycle. The spatial distribution ofsources closely mirrors data on fertilizer application with particularly large N2O sourcesover the US Cornbelt. Existing inventories for N2O predict emissions that differsubstantially from the inverse model results in both seasonal cycle and magnitude. Weestimate a total annual N2O budget over the central US of 0.9–1.2 TgN/yr and anextrapolated budget for the entire US and Canada of 2.1–2.6 TgN/yr. By this estimate, theUS and Canada account for 12–15% of the total global N2O source or 32–39% of the globalanthropogenic source as reported by the Intergovernmental Panel on Climate Change in2007