Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.400 IF 3.400
  • IF 5-year value: 3.841 IF 5-year
  • CiteScore value: 3.71 CiteScore
  • SNIP value: 1.472 SNIP 1.472
  • IPP value: 3.57 IPP 3.57
  • SJR value: 1.770 SJR 1.770
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 70 Scimago H
    index 70
  • h5-index value: 49 h5-index 49
Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 28 May 2019

Submitted as: research article | 28 May 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Measurement Techniques (AMT).

Evaluating the impact of spatial resolution on tropospheric NO2 column comparisons within urban areas using high-resolution airborne data

Laura M. Judd1,2, Jassim A. Al-Saadi1, Scott J. Janz3, Matthew G. Kowalewski3,4, R. Bradley Pierce5, James J. Szykman6, Lukas C. Valin6, Robert Swap3, Alexander Cede7, Moritz Mueller7,8, Martin Tiefengraber7,8, Nader Abuhassan3,9, and David Williams6 Laura M. Judd et al.
  • 1NASA Langley Research Center, Hampton, VA, 23681, USA
  • 2NASA Postdoctoral Program, Hampton, VA, 23681, USA
  • 3NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  • 4Universities Space Research Association, Columbia, MD, 21046, USA
  • 5University of Wisconsin-Madison Space Science and Engineering Center, Madison, WI, 53706, USA
  • 6United States Environmental Protection Agency Office of Research and Development, Triangle Research Park, NC, 27709, USA
  • 7LuftBlick, Kreith, Austria
  • 8Department of Atmospheric and Cryospheric Science, University of Innsbruck, Innsbruck, Austria
  • 9Joint Center for Earth Systems Technology, University of Maryland-Baltimore County, Baltimore, MD, 21228, USA

Abstract. NASA deployed an airborne UV/Visible spectrometer, GeoTASO, in May–June 2017 to produce high resolution (approximately 250 × 250 m), gapless NO2 datasets over the western shore of Lake Michigan and over the Los Angeles Basin. Results show that the airborne tropospheric vertical column retrievals compare well with ground-based Pandora spectrometer column NO2 observations (r2 = 0.91 and slope of 1.03). Apparent disagreements between the two measurements can be sensitive to the coincidence criteria and are often associated with large local variability, including rapid temporal changes and also spatial heterogeneity that may be observed differently by the sunward viewing Pandora observations. The gapless mapping strategy executed during the 2017 GeoTASO flights provides data suitable for averaging to coarser areal resolutions to simulate satellite retrievals. As simulated satellite pixel area increases to values typical of TEMPO, TROPOMI, and OMI, the agreement with Pandora measurements is degraded as localized polluted plumes observed by Pandora are spatially averaged over larger areas (aircraft-to-Pandora slope: TEMPO scale = 0.88; TROPOMI scale = 0.77; OMI scale = 0.57). This behavior suggests that satellite products are representative of individual Pandora observations up to a certain pollution scale that depends on satellite spatial resolution. In these two regions, Pandora and TEMPO or TROPOMI have the potential to compare well up to pollution scales of 30 x 1015 molecules cm−2. Two publicly available OMI tropospheric NO2 retrievals are both found to be biased low with respect to Pandora observations (NASA V3 Standard Product slope = 0.18 and Berkeley High Resolution Product slope = 0.30). However, the agreement improves when higher resolution a priori inputs are used for the tropospheric air mass factor calculation. Overall, this work explores best practices for satellite validation strategies by showing the sensitivity to product spatial resolution and demonstrates how the high spatial resolution NO2 data retrieved from airborne spectrometers, such as GeoTASO, can be used with high temporal resolution surface observations to evaluate the influence of spatial heterogeneity on validation results.

Laura M. Judd et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Laura M. Judd et al.
Laura M. Judd et al.
Total article views: 514 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
363 147 4 514 5 5
  • HTML: 363
  • PDF: 147
  • XML: 4
  • Total: 514
  • BibTeX: 5
  • EndNote: 5
Views and downloads (calculated since 28 May 2019)
Cumulative views and downloads (calculated since 28 May 2019)
Viewed (geographical distribution)  
Total article views: 390 (including HTML, PDF, and XML) Thereof 387 with geography defined and 3 with unknown origin.
Country # Views %
  • 1
No saved metrics found.
No discussed metrics found.
Latest update: 20 Sep 2019
Publications Copernicus
Short summary
In 2017, an airborne mapping spectrometer (GeoTASO) was used to observe high resolution column densities of nitrogen dioxide (NO2) over the western shore of Lake Michigan and the Los Angeles Basin. These data were used to simulate the spatial resolution of current and future satellite NO2 retrievals to evaluate the impact of pixel size on comparisons to ground-based observations in urban areas. As spatial resolution improves, the sensitivity to more heterogeneously polluted scenes increases.
In 2017, an airborne mapping spectrometer (GeoTASO) was used to observe high resolution column...