Evaluation of OMI operational standard NO2 column retrievals using in situ and surface-based NO2 observations
L. N. Lamsal1,2,N. A. Krotkov2,E. A. Celarier1,2,W. H. Swartz2,3,K. E. Pickering2,E. J. Bucsela4,J. F. Gleason2,R. V. Martin5,6,S. Philip5,H. Irie7,A. Cede2,8,J. Herman2,9,A. Weinheimer10,J. J. Szykman11,and T. N. Knepp12,13L. N. Lamsal et al. L. N. Lamsal1,2,N. A. Krotkov2,E. A. Celarier1,2,W. H. Swartz2,3,K. E. Pickering2,E. J. Bucsela4,J. F. Gleason2,R. V. Martin5,6,S. Philip5,H. Irie7,A. Cede2,8,J. Herman2,9,A. Weinheimer10,J. J. Szykman11,and T. N. Knepp12,13
1Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD 21046, USA
2NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
3Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
4SRI International, Menlo Park, CA 94025, USA
5Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 3J5, Canada
6Also at Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
7Center for Environmental Remote Sensing, Chiba University, 1–33, Yayoicho, Inage-ku, Chiba 263-8522, Japan
8LuftBlick, Kreith, Austria
9University of Maryland, Joint Center for Earth Systems Technology, Baltimore, MD 21228, USA
10National Center for Atmospheric Research, Boulder, CO 80307, USA
11United States Environmental Protection Agency Office of Research and Development, Hampton, VA 23681, USA
12Science Systems and Applications, Inc., Hampton, VA 23681, USA
13NASA Langley Research Center, Hampton, VA 23681, USA
1Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD 21046, USA
2NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
3Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
4SRI International, Menlo Park, CA 94025, USA
5Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, B3H 3J5, Canada
6Also at Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA
7Center for Environmental Remote Sensing, Chiba University, 1–33, Yayoicho, Inage-ku, Chiba 263-8522, Japan
8LuftBlick, Kreith, Austria
9University of Maryland, Joint Center for Earth Systems Technology, Baltimore, MD 21228, USA
10National Center for Atmospheric Research, Boulder, CO 80307, USA
11United States Environmental Protection Agency Office of Research and Development, Hampton, VA 23681, USA
12Science Systems and Applications, Inc., Hampton, VA 23681, USA
13NASA Langley Research Center, Hampton, VA 23681, USA
Received: 31 Mar 2014 – Discussion started: 05 Jun 2014 – Revised: 12 Sep 2014 – Accepted: 26 Sep 2014 – Published: 05 Nov 2014
Abstract. We assess the standard operational nitrogen dioxide (NO2) data product (OMNO2, version 2.1) retrieved from the Ozone Monitoring Instrument (OMI) onboard NASA's Aura satellite using a combination of aircraft and surface in~situ measurements as well as ground-based column measurements at several locations and a bottom-up NOx emission inventory over the continental US. Despite considerable sampling differences, NO2 vertical column densities from OMI are modestly correlated (r = 0.3–0.8) with in situ measurements of tropospheric NO2 from aircraft, ground-based observations of NO2 columns from MAX-DOAS and Pandora instruments, in situ surface NO2 measurements from photolytic converter instruments, and a bottom-up NOx emission inventory. Overall, OMI retrievals tend to be lower in urban regions and higher in remote areas, but generally agree with other measurements to within ± 20%. No consistent seasonal bias is evident. Contrasting results between different data sets reveal complexities behind NO2 validation. Since validation data sets are scarce and are limited in space and time, validation of the global product is still limited in scope by spatial and temporal coverage and retrieval conditions. Monthly mean vertical NO2 profile shapes from the Global Modeling Initiative (GMI) chemistry-transport model (CTM) used in the OMI retrievals are highly consistent with in situ aircraft measurements, but these measured profiles exhibit considerable day-to-day variation, affecting the retrieved daily NO2 columns by up to 40%. This assessment of OMI tropospheric NO2 columns, together with the comparison of OMI-retrieved and model-simulated NO2 columns, could offer diagnostic evaluation of the model.
