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Journal of Geophysical Research: Atmospheres

Airborne MAX-DOAS measurements over California: Testing the NASA OMI tropospheric NO2 product

Authors

  • Hilke Oetjen,

    1. Department of Chemistry and Biochemistry, University of Boulder, Boulder, Colorado, USA
    2. Now at the UCLA/JPL Joint Institute for Regional Earth System Science and Engineering, Los Angeles, California, USA
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  • Sunil Baidar,

    1. Department of Chemistry and Biochemistry, University of Boulder, Boulder, Colorado, USA
    2. Cooperative Institute for Research in Environmental Sciences, University of Boulder, Boulder, Colorado, USA
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  • Nickolay A. Krotkov,

    1. NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
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  • Lok N. Lamsal,

    1. NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
    2. Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, Maryland, USA
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  • Michael Lechner,

    1. Department of Chemistry and Biochemistry, University of Boulder, Boulder, Colorado, USA
    2. NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
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  • Rainer Volkamer

    Corresponding author
    1. Department of Chemistry and Biochemistry, University of Boulder, Boulder, Colorado, USA
    2. Cooperative Institute for Research in Environmental Sciences, University of Boulder, Boulder, Colorado, USA
    • Corresponding author: R. Volkamer, Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA. (rainer.volkamer@colorado.edu)

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Abstract

[1] Airborne Multi-AXis Differential Optical Absorption Spectroscopy (AMAX-DOAS) measurements of NO2 tropospheric vertical columns were performed over California for two months in summer 2010. The observations are compared to the NASA Ozone Monitoring Instrument (OMI) tropospheric vertical columns (data product v2.1) in two ways: (1) Median data were compared for the whole time period for selected boxes, and the agreement was found to be fair (R = 0.97, slope = 1.4 ± 0.1, N = 10). (2) A comparison was performed on the mean of coincident AMAX-DOAS measurements within the area of the corresponding OMI pixels with the tropospheric NASA OMI NO2 assigned to that pixel. The effects of different data filters were assessed. Excellent agreement and a strong correlation (R = 0.85, slope = 1.05 ± 0.09, N = 56) was found for (2) when the data were filtered to eliminate large pixels near the edge of the OMI orbit, the cloud radiance fraction was <50%, the OMI overpass occurred within 2 h of the AMAX-DOAS measurements, the flight altitude was >2 km, and a representative sample of the footprint was taken by the AMAX-DOAS instrument. The AMAX-DOAS and OMI data sets both show a reduction of NO2 tropospheric columns on weekends by 38 ± 24% and 33 ± 11%, respectively. The assumptions in the tropospheric satellite air mass factor simulations were tested using independent measurements of surface albedo, aerosol extinction, and NO2 profiles for Los Angeles for July 2010 indicating an uncertainty of 12%.

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