Sources of nitrous oxide, an important greenhouse gas, over the central United States

Nitrous oxide (N₂O) is the third-largest long-lived greenhouse gas in terms of radiative forcing, but knowledge of N₂O sources over the United States is highly uncertain. We present top-down constraints on the magnitude, spatial distribution, and seasonality of N₂O emissions over the central United States. We pair data from aircraft measurements and tall towers in 2004 and 2008 with a high-resolution back-trajectory model known as STILT. Our results indicate a seasonal cycle and magnitude of emissions lacking in existing inventories. The spatial distribution of sources closely mirrors data on fertilizer application with particularly large N₂O sources over the U.S. Corn Belt.