Document Type

Article

Publication Date

7-18-2017

Publication Title

Atmospheric Chemistry and Physics

ISSN

1680-7316

Volume

17

Issue

14

DOI

https://doi.org/10.5194/acp-17-8725-2017

Abstract

Glyoxal (CHOCHO) is produced in the atmosphere by the oxidation of volatile organic compounds (VOCs). Like formaldehyde (HCHO), another VOC oxidation product, it is measurable from space by solar backscatter. Isoprene emitted by vegetation is the dominant source of CHOCHO and HCHO in most of the world. We use aircraft observations of CHOCHO and HCHO from the SENEX campaign over the southeast US in summer 2013 to better understand the CHOCHO time-dependent yield from isoprene oxidation, its dependence on nitrogen oxides (NOx  ≡  NO + NO2), the behavior of the CHOCHO–HCHO relationship, the quality of OMI CHOCHO satellite observations, and the implications for using CHOCHO observations from space as constraints on isoprene emissions. We simulate the SENEX and OMI observations with the Goddard Earth Observing System chemical transport model (GEOS-Chem) featuring a new chemical mechanism for CHOCHO formation from isoprene. The mechanism includes prompt CHOCHO formation under low-NOx conditions following the isomerization of the isoprene peroxy radical (ISOPO2). The SENEX observations provide support for this prompt CHOCHO formation pathway, and are generally consistent with the GEOS-Chem mechanism. Boundary layer CHOCHO and HCHO are strongly correlated in the observations and the model, with some departure under low-NOx conditions due to prompt CHOCHO formation. SENEX vertical profiles indicate a free-tropospheric CHOCHO background that is absent from the model. The OMI CHOCHO data provide some support for this free-tropospheric background and show southeast US enhancements consistent with the isoprene source but a factor of 2 too low. Part of this OMI bias is due to excessive surface reflectivities assumed in the retrieval. The OMI CHOCHO and HCHO seasonal data over the southeast US are tightly correlated and provide redundant proxies of isoprene emissions. Higher temporal resolution in future geostationary satellite observations may enable detection of the prompt CHOCHO production under low-NOx conditions apparent in the SENEX data.

Comments

C. Chan Miller (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA)
D. J. Jacob (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA)
D. J. Jacob (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
E. A. Marais (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA)
K. Yu (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
K. R. Travis (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
P. S. Kim (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA)
J. A. Fisher (School of Chemistry and School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, Australia)
L. Zhu (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
G. M. Wolfe (Atmospheric Chemistry and Dynamics Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA)
G. M. Wolfe (Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD, USA)
T. F. Hanisco (Atmospheric Chemistry and Dynamics Lab, NASA Goddard Space Flight Center, Greenbelt, MD, USA)
F. N. Keutsch (School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
F. N. Keutsch (Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA)
J. Kaiser (Department of Chemistry, University of Wisconsin Madison, Madison, WI, USA)
J. Kaiser (now at: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA)
K.-E. Min (Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA)
K.-E. Min (Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, USA)
K.-E. Min (now at: School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju, South Korea)
S. S. Brown (Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, USA)
S. S. Brown (Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA)
R. A. Washenfelder (Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA)
R. A. Washenfelder (Chemical Sciences Division, NOAA Earth System Research Laboratory, Boulder, CO, USA)
G. González Abad (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA)
K. Chance (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA)

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Creative Commons Attribution 3.0 License
This work is licensed under a Creative Commons Attribution 3.0 License.

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