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Preprints
https://doi.org/10.5194/essd-2020-114
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/essd-2020-114
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  03 Jul 2020

03 Jul 2020

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This preprint is currently under review for the journal ESSD.

A Decade of GOSAT Proxy Satellite CH4 Observations

Robert J. Parker1,2, Alex Webb1,2, Hartmut Boesch1,2, Peter Somkuti3, Rocio Barrio Guillo1,2, Antonio Di Noia2, Nikoleta Kalaitzi1,2, Jasdeep Anand2, Peter Bergamaschi4, Frederic Chevallier5, Paul I. Palmer6,7, Liang Feng6,7, Nicholas M. Deutscher8, Dietrich G. Feist9,10,11, David W. T. Griffith8, Frank Hase12, Rigel Kivi13, Isamu Morino14, Justus Notholt15, Young-Suk Oh16, Hirofumi Ohyama14, Christof Petri15, David F. Pollard17, Coleen Roehl18, Mahesh K. Sha19, Kei Shiomi20, Kimberly Strong21, Ralf Sussmann22, Yao Te23, Voltaire A. Velazco8, Thorsten Warneke15, Paul O. Wennberg18, and Debra Wunch24 Robert J. Parker et al.
  • 1National Centre for Earth Observation, University of Leicester, UK
  • 2Earth Observation Science, School of Physics and Astronomy, University of Leicester, UK
  • 3Cooperative Institute for Research in the Atmosphere, Colorado State University, Colorado, US
  • 4European Commission Joint Research Centre, Ispra (Va), Italy
  • 5Laboratoire des Sciences du Climat et de L’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif Sur Yvette, France
  • 6School of GeoSciences, University of Edinburgh, Edinburgh, Scotland
  • 7National Centre for Earth Observation, University of Edinburgh, Edinburgh, Scotland
  • 8Centre for Atmospheric Chemistry, School of Earth, Atmospheric and Life Sciences, University of Wollongong
  • 9Lehrstuhl für Physik der Atmosphäre, Ludwig-Maximilians-Universität München, Munich, Germany
  • 10Institut für Physik der Atmosphäre, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen, Germany
  • 11Max Planck Institute for Biogeochemistry, Jena, Germany
  • 12Karlsruhe Institute of Technology, IMK-ASF, Karlsruhe, Germany
  • 13Space and Earth Observation Centre, Finnish Meteorological Institute, Finland
  • 14National Institute for Environmental Studies (NIES), Tsukuba, Japan
  • 15Institute of Environmental Physics, University of Bremen, Germany
  • 16Climate Research Division, National Institute of Meteorological Sciences (NIMS), Jeju-do 63568, Republic of Korea
  • 17National Institute of Water and Atmospheric Research Ltd (NIWA), Lauder, New Zealand
  • 18California Institute of Technology, Pasadena, CA 91125, USA
  • 19Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 20Earth Observation Research Center, Japan Aerospace Exploration Agency, Japan
  • 21Department of Physics, University of Toronto, Canada
  • 22Karlsruhe Institute of Technology, IMK-IFU, Garmisch-Partenkirchen, Germany
  • 23Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères (LERMA-IPSL), Sorbonne Université, CNRS, Observatoire de Paris, PSL Université, 75005 Paris, France
  • 24Department of Physics, University of Toronto, Toronto, Canada

Abstract. This work presents the latest release (v9.0) of the University of Leicester GOSAT Proxy XCH4 dataset. Since the launch of the GOSAT satellite in 2009, this data has been produced by the UK National Centre for Earth Observation (NCEO) as part of the ESA Greenhouse Gas Climate Change Initiative (GHG-CCI) and Copernicus Climate Change Services (C3S) projects. With now over a decade of observations, we outline the many scientific studies achieved using past versions of this data in order to highlight how this latest version may be used in the future.

We describe in detail how the data is generated, providing information and statistics for the entire processing chain from the L1B spectral data through to the final quality-filtered column-averaged dry-air mole fraction (XCH4) data. We show that out of the 19.5 million observations made between April 2009 and December 2019, we determine that 7.3 million of these are sufficiently cloud-free (37.6 %) to process further and ultimately obtain 4.6 million (23.5 %) high-quality XCH4 observations. We separate these totals by observation mode (land and ocean sun-glint) and by month, to provide data users with the expected data coverage, including highlighting periods with reduced observations due to instrumental issues.

We perform extensive validation of the data against the Total Carbon Column Observing Network (TCCON), comparing to ground-based observations at 22 locations worldwide. We find excellent agreement to TCCON, with an overall correlation coefficient of 0.92 for the 88,345 co-located measurements. The single measurement precision is found to be 13.72 ppb and an overall global bias of 9.06 ppb is determined and removed from the Proxy XCH4 data. Additionally, we validate the separate components of the Proxy (namely the modelled XCO2 and the XCH4/XCO2 ratio) and find these to be in excellent agreement with TCCON.

In order to show the utility of the data for future studies, we compare against simulated XCH4 from the TM5 model. We find a high degree of consistency between the model and observations throughout both space and time. When focusing on specific regions, we find average differences ranging from just 3.9 ppb to 15.4 ppb. We find the phase and magnitude of the seasonal cycle to be in excellent agreement, with an average correlation coefficient of 0.93 and a mean seasonal cycle amplitude difference across all regions of −0.84 ppb.

This data is available at https://doi.org/10.5285/18ef8247f52a4cb6a14013f8235cc1eb (Parker and Boesch, 2020).

Robert J. Parker et al.

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Robert J. Parker et al.

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University of Leicester GOSAT Proxy XCH4 v9.0 R. J. Parker and H. Boesch https://doi.org/10.5285/18ef8247f52a4cb6a14013f8235cc1eb

Robert J. Parker et al.

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Short summary
This work presents the latest release of the University of Leicester GOSAT methane data and acts as the definitive description of this dataset. We detail the processing, validation and evaluation involved in producing this data and highlight its many applications. With now over a decade of global atmospheric methane observations, this dataset has helped, and will continue to help, us better understand the global methane budget and investigate how it may respond to a future changing climate.
This work presents the latest release of the University of Leicester GOSAT methane data and acts...
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