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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/amt-2019-174
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2019-174
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 25 Jun 2019

Research article | 25 Jun 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Measurement Techniques (AMT).

A Comparative Evaluation of Aura-OMI and SKYNET Near-UV Single-scattering Albedo Products

Hiren Jethva1,2 and Omar Torres2 Hiren Jethva and Omar Torres
  • 1Universities Space Research Association, Columbia, MD 21044, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Abstract. The aerosol single-scattering albedo (SSA) retrieved by the near-UV algorithm applied to the Aura/Ozone Monitoring Instrument (OMI) measurements (OMAERUV) is compared with an independent inversion product derived from the sky radiometer network SKYNET-a ground-based radiation observation network span over Asia and Europe. The present work continues our efforts to evaluate the consistency between the retrieved SSA from satellite and ground sensors. The automated spectral measurements of direct downwelling solar flux and sky radiances made by SKYNET Sun-sky radiometer are used as input to an inversion algorithm that derives spectral aerosol optical depth (AOD) and single-scattering albedo (SSA) in the near-UV to near-IR spectral range. The availability of SKYNET SSA measurements in the ultraviolet region of the spectrum allows, for the first time, a direct comparison with OMI SSA retrievals eliminating the need of extrapolating the satellite retrievals to the visible wavelengths as the case in the evaluation against the Aerosol Robotic Network (AERONET). An analysis of the collocated retrievals from over 25 SKYNET sites reveals that about 61 % (84 %) of OMI-SKYNET matchups agree within the absolute difference of ± 0.03 (± 0.05) for carbonaceous aerosols, 50 % (72 %) for dust aerosols, 45 % (75 %) for urban-industrial aerosol types. Regionally, the agreement between the two inversion products was robust over several sites in Japan influenced by carbonaceous and urban-industrial aerosols, at the biomass burning site Phimai in Thailand, and polluted urban site in New Delhi, India. The collocated dataset yields fewer matchups identified as dust aerosols mostly over the site Dunhuang with more than half of the matchup points confined to within ± 0.03 limits. Combinedly, the OMI-SKYNET retrievals agree mostly within ± 0.03 for the AOD (388 or 400 nm) larger than 0.5 and UV Aerosol Index larger than 0.2. The remaining uncertainties in both inversion products can be attributed to specific assumptions made in the retrieval algorithms, i.e., the uncertain calibration constant, assumption of spectral surface albedo and particle shape, and sub-pixel cloud contamination. The assumption of fixed and spectrally neutral surface albedo (0.1) in the SKYNET inversion appears to be unrealistic, leading to a large underestimation of retrieved SSA, especially for low aerosol load conditions. At large AOD values for carbonaceous and dust aerosols, however, retrieved SSA values by the two independent inversion methods are generally consistent in spite of the differences in retrieval approaches.

Hiren Jethva and Omar Torres
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Status: open (until 20 Aug 2019)
Status: open (until 20 Aug 2019)
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Hiren Jethva and Omar Torres
Hiren Jethva and Omar Torres
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Short summary
The intercomparison of satellite and ground measured aerosol absorption properties, such as presented here using Aura-OMI and SKYNET sensors, constitutes an important exercise to evaluate relative performance, track algorithm changes, and useful to diagnose retrieval accuracy and issues. The two datasets are found to agree reasonably well under moderate to higher aerosol loading but show disagreement under lower aerosol amounts due to retrieval issues in both techniques.
The intercomparison of satellite and ground measured aerosol absorption properties, such as...
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