Evaluation of space‐based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America

We retrieve tropospheric nitrogen dioxide (NO 2 ) columns for May 2004 to April 2005 from the SCIAMACHY satellite instrument to derive top‐down emissions of nitrogen oxides (NO x = NO + NO 2 ) via inverse modeling with a global chemical transport model (GEOS‐Chem). Simulated NO 2 vertical profiles used in the retrieval are evaluated with airborne measurements over and downwind of North America (ICARTT); a northern midlatitude lightning source of 1.6 Tg N yr −1 minimizes bias in the retrieval. Retrieved NO 2 columns are validated (r 2 = 0.60, slope = 0.82) with coincident airborne in situ measurements. The top‐down emissions are combined with a priori information from a bottom‐up emission inventory with error weighting to achieve an improved a posteriori estimate of the global distribution of surface NO x emissions. Our a posteriori NO x emission inventory for land surface NO x emissions (46.1 Tg N yr −1 ) is 22% larger than the GEIA‐based a priori bottom‐up inventory for 1998, a difference that reflects rising anthropogenic emissions, especially from East Asia. A posteriori NO x emissions for East Asia (9.8 Tg N yr −1 ) exceed those from other continents. The a posteriori inventory improves the GEOS‐Chem simulation of NO x , peroxyacetylnitrate, and nitric acid with respect to airborne in situ measurements over and downwind of New York City. The a posteriori is 7% larger than the EDGAR 3.2FT2000 global inventory, 3% larger than the NEI99 inventory for the United States, and 68% larger than a regional inventory for 2000 for eastern Asia. SCIAMACHY NO 2 columns over the North Atlantic show a weak plume from lightning NO x .