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Volume 16, issue 21
Atmos. Chem. Phys., 16, 13477-13490, 2016
https://doi.org/10.5194/acp-16-13477-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 13477-13490, 2016
https://doi.org/10.5194/acp-16-13477-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 01 Nov 2016

Research article | 01 Nov 2016

Observing atmospheric formaldehyde (HCHO) from space: validation and intercomparison of six retrievals from four satellites (OMI, GOME2A, GOME2B, OMPS) with SEAC4RS aircraft observations over the southeast US

Lei Zhu1, Daniel J. Jacob1,2, Patrick S. Kim2, Jenny A. Fisher3,4, Karen Yu1, Katherine R. Travis1, Loretta J. Mickley1, Robert M. Yantosca1, Melissa P. Sulprizio1, Isabelle De Smedt5, Gonzalo González Abad6, Kelly Chance6, Can Li7,8, Richard Ferrare9, Alan Fried10, Johnathan W. Hair9, Thomas F. Hanisco8, Dirk Richter10, Amy Jo Scarino11, James Walega10, Petter Weibring10, and Glenn M. Wolfe8,12 Lei Zhu et al.
  • 1John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
  • 3Centre for Atmospheric Chemistry, School of Chemistry, University of Wollongong, Wollongong, NSW, Australia
  • 4School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, Australia
  • 5Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 6Harvard–Smithsonian Center for Astrophysics, Cambridge, MA, USA
  • 7Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, USA
  • 8NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 9NASA Langley Research Center, Hampton, VA 23681, USA
  • 10Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
  • 11Science Systems and Applications, Inc., Hampton, VA, USA
  • 12Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA

Abstract. Formaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs), but validation of the data has been extremely limited. Here we use highly accurate HCHO aircraft observations from the NASA SEAC4RS (Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys) campaign over the southeast US in August–September 2013 to validate and intercompare six retrievals of HCHO columns from four different satellite instruments (OMI, GOME2A, GOME2B and OMPS; for clarification of these and other abbreviations used in the paper, please refer to Appendix A) and three different research groups. The GEOS-Chem chemical transport model is used as a common intercomparison platform. All retrievals feature a HCHO maximum over Arkansas and Louisiana, consistent with the aircraft observations and reflecting high emissions of biogenic isoprene. The retrievals are also interconsistent in their spatial variability over the southeast US (r = 0.4–0.8 on a 0.5° × 0.5° grid) and in their day-to-day variability (r = 0.5–0.8). However, all retrievals are biased low in the mean by 20–51%, which would lead to corresponding bias in estimates of isoprene emissions from the satellite data. The smallest bias is for OMI-BIRA, which has high corrected slant columns relative to the other retrievals and low scattering weights in its air mass factor (AMF) calculation. OMI-BIRA has systematic error in its assumed vertical HCHO shape profiles for the AMF calculation, and correcting this would eliminate its bias relative to the SEAC4RS data. Our results support the use of satellite HCHO data as a quantitative proxy for isoprene emission after correction of the low mean bias. There is no evident pattern in the bias, suggesting that a uniform correction factor may be applied to the data until better understanding is achieved.

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HCHO column data are widely used as a proxy for VOCs emissions, but validation of the data has been extremely limited. We use accurate aircraft observations to validate and intercompare 6 HCHO retrievals with GEOS-Chem as the intercomparison platform. Retrievals are interconsistent in spatial variability over the SE US and in daily variability, but are biased low by 20–51 %. Our work supports the use of HCHO column as a quantitative proxy for isoprene emission after correction of the low bias.
HCHO column data are widely used as a proxy for VOCs emissions, but validation of the data has...
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