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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/amt-2020-281
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2020-281
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  05 Aug 2020

05 Aug 2020

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This preprint is currently under review for the journal AMT.

Methane retrieved from TROPOMI: improvement of the data product and validation of the first two years of measurements

Alba Lorente1, Tobias Borsdorff1, Andre Butz2,3, Otto Hasekamp1, Joost aan de Brugh1, Andreas Schneider1, Frank Hase4, Rigel Kivi5, Debra Wunch6, David F. Pollard7, Kei Shiomi8, Nicholas M. Deutscher9, Voltaire A. Velazco9, Coleen M. Roehl10, Paul O. Wennberg10, Thorsten Warneke11, and Jochen Landgraf1 Alba Lorente et al.
  • 1Earth science group, SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
  • 2Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany
  • 3Heidelberg Center for the Environment, University of Heidelberg, Heidelberg, Germany
  • 4Institute of Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 5Greenhouse Gases and Satellite Methods group, Finnish Meteorological Institute, Sodankylä, Finland
  • 6Department of Physics, University of Toronto, Toronto, Canada
  • 7National Institute of Water and Atmospheric Research Ltd (NIWA), Lauder, New Zealand
  • 8Japan Aerospace Exploration Agency (JAXA), Tsukuba, Japan
  • 9Centre for Atmospheric Chemistry, School of Earth, Atmospheric and Life Sciences, University of Wollongong,Wollongong, NSW, 2522
  • 10Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA
  • 11Institute of Environmental Physics, University of Bremen, Bremen, Germany

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) aboard of the Sentinel 5 Precursor (S5-P) satellite provides methane (CH4) measurements with high accuracy and exceptional temporal and spatial resolution. TROPOMI CH4 measurements are highly valuable to constrain emissions inventories and for trend analysis, with strict requirements on the data quality. This study describes the improvements that we have implemented to retrieve CH4 from TROPOMI using the RemoTeC full-physics algorithm. The updated TROPOMI CH4 product features a constant regularization scheme of the inversion that stabilizes the retrieval and yields less scatter in the data, and includes a higher resolution surface altitude database. We have tested the impact of three state-of-the-art molecular spectroscopic databases (HITRAN 2008, HITRAN 2016 and Scientific Exploitation of Operational Missions – Improved Atmospheric Spectroscopy Databases SEOM-IAS) and found that SEOM-IAS provides the best fitting results. The most relevant update in the TROPOMI XCH4 data product is the implementation of a posteriori correction fully independent of any reference data that is more accurate and corrects for the underestimation at low surface albedo scenes and the overestimation at high surface albedo scenes. After applying the correction, the albedo dependence is removed to a large extent in the TROPOMI versus satellite (Greenhouse gases Observing SATellite – GOSAT) and TROPOMI versus ground-based observations (Total Carbon Column Observing Network – TCCON) comparison, which is an independent verification of the correction scheme. We validate two years of TROPOMI CH4 data that shows the good agreement of the updated TROPOMI CH4 with TCCON (−3.4 ± 5.6 ppb) and GOSAT (−10.3 ± 16.8 pbb) (mean bias and standard deviation). Low and high albedo scenes as well as snow covered scenes are the most challenging for the CH4 retrieval algorithm, and although the posteriori correction accounts for most of the bias, there is a need to further investigate the underlying cause.

Alba Lorente et al.

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Alba Lorente et al.

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Short summary
TROPOMI aboard Sentinel-5P satellite provides methane (CH4) measurements with exceptional temporal and spatial resolution. This study describes a series of improvements developed to retrieve CH4 from TROPOMI. The updated CH4 product features (among others) a more accurate posteriori correction derived independently of any reference data. The validation of the improved data product shows good agreement with ground-based and satellite measurements, which highlights the quality of the TROPOMI CH4.
TROPOMI aboard Sentinel-5P satellite provides methane (CH4) measurements with exceptional...
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