Surface and lightning sources of nitrogen oxides over the United States: Magnitudes, chemical evolution, and outflow

Authors

R C. Hudman, Harvard University
D J. Jacob, Harvard University
S Turquety, Harvard UniversityFollow
Eric M. Leibensperger, Harvard University
L T. Murray, Harvard University
S Wu, Harvard University
A B. Gilliland, NOAA
M A. Avery, NASAFollow
T H. Bertram, University of California - Berkeley
William H. Brune, Pennsylvania State University - Main Campus
Ronald C. Cohen, University of California - Berkeley
Jack E. Dibb, University of New HampshireFollow
F Flocke, National Center for Atmospheric Research
A Fried, University of Colorado Boulder
J S. Holloway, University of Colorado Boulder
J A. Neuman, University of Colorado Boulder
R Orville, Texas A & M University - College Station
A E. Perring, University of California - BerkeleyFollow
Xinrong Ren, NOAA
G W. Sachse, NASA Langley Research CenterFollow
H B. Singh, NASA
Aaron L. Swanson, University of California, Irvine
Paul J. Wooldridge, University of California - Berkeley

Abstract

We use observations from two aircraft during the ICARTT campaign over the eastern United States and North Atlantic during summer 2004, interpreted with a global 3-D model of tropospheric chemistry (GEOS-Chem) to test current understanding of regional sources, chemical evolution, and export of NOx. The boundary layer NOx data provide top-down verification of a 50% decrease in power plant and industry NOx emissions over the eastern United States between 1999 and 2004. Observed NOx concentrations at 8–12 km altitude were 0.55 ± 0.36 ppbv, much larger than in previous U.S. aircraft campaigns (ELCHEM, SUCCESS, SONEX) though consistent with data from the NOXAR program aboard commercial aircraft. We show that regional lightning is the dominant source of this upper tropospheric NOx and increases upper tropospheric ozone by 10 ppbv. Simulating ICARTT upper tropospheric NOx observations with GEOS-Chem requires a factor of 4 increase in modeled NOx yield per flash (to 500 mol/ flash). Observed OH concentrations were a factor of 2 lower than can be explained from current photochemical models, for reasons that are unclear. A NOy-CO correlation analysis of the fraction f of North American NOx emissions vented to the free troposphere as NOy (sum of NOx and its oxidation products) shows observed f = 16 ± 10% and modeled f = 14 ± 9%, consistent with previous studies. Export to the lower free troposphere is mostly HNO3 but at higher altitudes is mostly PAN. The model successfully simulates NOy export efficiency and speciation, supporting previous model estimates of a large U.S. anthropogenic contribution to global tropospheric ozone through PAN export.

Department

Earth Sciences, Earth Systems Research Center

Publication Date

6-27-2007

Journal Title

Journal of Geophysical Research

Publisher

Wiley

Digital Object Identifier (DOI)

10.1029/2006JD007912

Document Type

Article

Recommended Citation

Hudman, R. C., et al. (2007), Surface and lightning sources of nitrogen oxides over the United States: Magnitudes, chemical evolution, and outflow, J. Geophys. Res., 112, D12S05, doi:10.1029/2006JD007912.

Rights

Copyright 2007 by the American Geophysical Union.