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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-382
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Jun 2017
Review status
This discussion paper is a preprint. It has been under review for the journal Atmospheric Chemistry and Physics (ACP). A final paper in ACP is not foreseen.
Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States
Zhe Jiang1, Helen Worden1, John R. Worden2, Daven K. Henze3, Dylan B. A. Jones4, Avelino F. Arellano5, Emily V. Fischer6, Liye Zhu6, Kazuyuki Miyazaki2,7, K. Folkert Boersma8,9, and Vivienne H. Payne2 1National Center for Atmospheric Research, Boulder, CO, USA
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
3Department of Mechanical Engineering, University of Colorado, Boulder, CO, USA
4Department of Physics, University of Toronto, Toronto, ON, Canada
5Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
6Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA
7Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
8Wageningen University, Meteorological and Air Quality department, Wageningen, the Netherlands
9Royal Netherlands Meteorological Institute, De Bilt, The Netherlands
Abstract. Decreases in surface emissions of nitrogen oxides (NOx = NO + NO2) in North America have led to substantial improvements in air-quality over the last several decades. Here we show that satellite observations of tropospheric nitrogen dioxide (NO2) columns over the contiguous United States (US) do not decrease after about 2009, while surface NO2 concentrations continue to decline through to the present. This divergence, if it continues, could have a substantial impact on surface air quality due to mixing of free-tropospheric air into the boundary layer. Our results show only limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, but we do find a possible relationship of NO2 changes to decadal climate variability. Our analysis demonstrates that the intensity of transpacific transport is stronger in El Niño years and weaker in La Niña years, and consequently, that decadal-scale climate variability impacts the contribution of Asian emissions on North American atmospheric composition. Because of the short lifetime, it is usually believed that the direct contribution of long-range transport to tropospheric NOx distribution is limited. If our hypothesis about transported Asian emissions is correct, then this observed divergence between satellite and surface NOx could indicate mechanisms that allow for either NOx or its reservoir species to have a larger than expected effect on North American tropospheric composition. These results therefore suggest more aircraft and satellite studies to determine the possible missing processes in our understanding of the long-range transport of tropospheric NOx.

Citation: Jiang, Z., Worden, H., Worden, J. R., Henze, D. K., Jones, D. B. A., Arellano, A. F., Fischer, E. V., Zhu, L., Miyazaki, K., Boersma, K. F., and Payne, V. H.: Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-382, 2017.
Zhe Jiang et al.
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Zhe Jiang et al.
Zhe Jiang et al.

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Short summary
We investigated the variation of US tropospheric NO2 in the past decade. We demonstrated significant divergence between the time variation in tropospheric NO2 columns from OMI retrievals and surface measurements. Our analysis suggests limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, and indicates possible important contributions from long-range transport of Asian emissions that are modulated by ENSO.
We investigated the variation of US tropospheric NO2 in the past decade. We demonstrated...
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