Preprints
https://doi.org/10.5194/acp-2020-1207
https://doi.org/10.5194/acp-2020-1207

  07 Dec 2020

07 Dec 2020

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

AEROCOM/AEROSAT AAOT & SSA study, part I: evaluation and intercomparison of satellite measurements

Nick Schutgens1, Oleg Dubovik2, Otto Hasekamp3, Omar Torres4, Hiren Jethva5, Peter J. T. Leonard6, Pavel Litvinov2, Jens Redemann7, Yohei Shinozuka8,9, Gerrit de Leeuw10,a, Stefan Kinne11, Thomas Popp12, Michael Schulz13, and Philip Stier14 Nick Schutgens et al.
  • 1Department of Earth Science, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
  • 2Laboratoire d’Optique Atmosphérique, CNRS/Université Lille, Villeneuve d’Ascq, France
  • 3SRON Netherlands Institute for Space Research, Utrecht, The Netherlands
  • 4Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 5Universities Space Research Association-GESTAR, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 6ADNET Systems, Inc., Suite A100, 7515 Mission Drive, Lanham, MD 20706, USA
  • 7School of Meteorology , University of Oklahoma, Norman, USA
  • 8Universities Space Research Association, Columbia, Maryland, USA
  • 9NASA Ames Research Center, Moffett Field, California, USA
  • 10Finnish Meteorological Institute (FMI), Climate Research Programme, Helsinki, Finland
  • 11Max-Planck-Institut für Meteorologie, D-20146 Hamburg, Germany
  • 12German Aerospace Center (DLR), German Remote Sensing Data Center Atmosphere, Oberpfaffenhofen, Germany
  • 13Norwegian Meteorological Institute, P.O.Box 43, Blindern, 0313 Oslo, Norway
  • 14Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UK
  • acurrently at: Royal Netherlands Meteorological Institute (KNMI), R&D Satellite Observations, De Bilt, the Netherlands

Abstract. Global measurements of absorptive aerosol optical depth (AAOD) are scarce and mostly provided by the ground network AERONET (AErosol RObotic NETwork). In recent years, several satellite products of AAOD have appeared. This study's primary aim is to establish the usefulness of these datasets for AEROCOM (AEROsol Comparisons between Observations and Models) model evaluation with a focus on the years 2006, 2008 and 2010. The satellite products are super-observations consisting of 1° × 1° × 30min aggregated retrievals.

This study consist of two parts: 1) an assessment of satellite datasets; 2) their application to the evaluation of AEROCOM models. The current paper describes the first part and details an evaluation with AERONET observations from the sparse AERONET network as well as a global intercomparison of satellite datasets, with a focus on how minimum AOD (Aerosol Optical Depth) thresholds and temporal averaging may improve agreement.

All satellite datasets are shown to have reasonable skill for AAOD (3 out of 4 datasets show correlations with AERONET in excess of 0.6) but less skill for SSA (Single Scattering Albedo; only 1 out of 4 datasets shows correlations with AERONET in excess of 0.6). In comparison, satellite AOD shows correlations from 0.72 to 0.88 against the same AERONET dataset. We do show that performance vs. AERONET and satellite agreements for SSA significantly improve at higher AOD. Temporal averaging also improves agreements between satellite datasets. Nevertheless multi-annual averages still show systematic differences, even at high AOD. In particular, we show that two POLDER products appear to have a systematic SSA difference over land of about 0.04, independent of AOD. Identifying the cause of this bias offers the possibility of substantially improving current datasets.

We also provide evidence that suggests that evaluation with AERONET observations leads to an underestimate of true biases in satellite SSA.

In the second part of this study we show that, notwithstanding these biases in satellite AAOD and SSA, the datasets allow meaningful evaluation of AEROCOM models.

Nick Schutgens et al.

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Nick Schutgens et al.

Nick Schutgens et al.

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Short summary
Absorptive aerosol has a potentially large impact on climate change. We evaluate and intercompare four global satellite datasets of Absorptive Aerosol Optical Depth (AAOD) and Single Scattering Albedo (SSA). We show that these datasets show reasonable correlations with the AERONET reference although significant biases remain. In a follow-up paper we show that these observations nevertheless can be used for model evaluation.
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