Preprints
https://doi.org/10.5194/amt-2020-173
https://doi.org/10.5194/amt-2020-173

  23 Jun 2020

23 Jun 2020

Review status: this preprint was under review for the journal AMT. A revision for further review has not been submitted.

Diurnal variability of total column NO2 measured using direct solar and lunar spectra over Table Mountain, California (34.38° N)

King-Fai Li1, Ryan Khoury1, Thomas J. Pongetti2, Stanley P. Sander2, and Yuk L. Yung2,3 King-Fai Li et al.
  • 1Department of Environmental Science, University of California, Riverside, California, USA
  • 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
  • 3Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA

Abstract. A full diurnal measurement of total column NO2 has been made over the Jet Propulsion Laboratory’s Table Mountain Facility (TMF) located in the mountains above Los Angeles, California, USA (2.286 km above mean sea level, 34.38° N, 117.68° W). During a representative week in October 2018, a grating spectrometer measured the telluric NO2 absorptions in direct solar and lunar spectra. The total column NO2 is retrieved using a model-based minimum-amount Langley extrapolation, which enables us to accurately treat the non-constant NO2 diurnal cycle abundance and the effects of pollution near the measurement site. The measured 24-hour cycle of total column NO2 on clean days agrees with a 1-D photochemical model calculation, including the monotonic changes during daytime and nighttime due to the exchange with the N2O5 reservoir and the abrupt changes at sunrise and sunset due to the activation or deactivation of the NO2 photodissociation. The observed daytime NO2 increasing rate is (1.29 ± 0.30)×1014 cm−2 h−1. The total column NO2 in one of the afternoons during the measurement period was much higher than the model simulation, implying the influence of urban pollution from nearby cities. A 24-hour back-trajectory analysis shows that the wind first came from inland in the northeast and reached the southern Los Angeles before it turned northeast and finally arrived TMF, allowing it to pick up pollutants from Riverside County, Orange County, and Downtown Los Angeles.

King-Fai Li et al.

 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

King-Fai Li et al.

King-Fai Li et al.

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Short summary
Nitrogen dioxide (NO2) plays a dominant role in the stratospheric ozone-destroying catalytic cycle. We have retrieved the diurnal cycle of NO2 column over the Table Mountain in Southern California, USA during a week of October 2018. Under clean condition, we are able to predict the diurnal cycle using standard photochemistry. On a day with significant pollution, we see the effect of NO2 sources in the nearby Los Angeles Basin.