A decade of GOSAT Proxy satellite CH4 observations

Robert J. Parker (1, 2) , Alex J. Webb (1, 2) , Hartmut Boesch (3, 2) , Peter Somkuti (4) , Rocio Barrio Guillo (1, 2) , Antonio Di Noia (2) , Nikoleta Kalaitzi (1, 2) , Jasdeep S. Anand (2) , Peter Bergamaschi (5) , Frédéric Chevallier (6, 7) , Paul I. Palmer (8, 9) , Liang Feng (8, 9) , N. M. Deutscher (10) , Dietrich G. Feist (11, 12, 13) , David W.T. Griffith (10) , Frank Hase (14) , Rigel Kivi (15) , Isamu Morino (16) , Justus Notholt (17) , Young-Suk Oh (18) , Hirofumi Ohyama (16) , Christof Petri (17) , David F. Pollard (19) , Coleen M. Roehl (20) , Mahesh Kumar Sha (21) , Kei Shiomi (22) , Kimberly Strong (23) , Ralf Sussmann (24) , Yao Veng Té (25) , Voltaire A. Velazco (10) , Thorsten Warneke (17) , Paul O. Wennberg (20) , Debra Wunch (23)

1 University of Leicester
2 EOS - Earth Observation Science Group [Leicester]
3 University Hospitals Leicester
4 CIRA - Cooperative Institute for Research in the Atmosphere
5 JRC - European Commission - Joint Research Centre [Ispra]
6 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
7 SATINV - Modélisation INVerse pour les mesures atmosphériques et SATellitaires
8 School of Geosciences [Edinburgh]
9 NCEO - NERC National Centre for Earth Observation
10 University of Wollongong [Australia]
11 LMU - Ludwig Maximilian University [Munich] = Ludwig Maximilians Universität München
12 IPA - DLR Institut für Physik der Atmosphäre = DLR Institute of Atmospheric Physics
13 MPI-BGC - Max Planck Institute for Biogeochemistry
14 INT - Institute of Nanotechnology [Karlsruhe]
15 Space and Earth Observation Centre [Sodankylä]
16 NIES - National Institute for Environmental Studies
17 IUP - Institute of Environmental Physics [Bremen]
18 NIMS - National Institute of Meteorological Sciences
19 NIWA - National Institute of Water and Atmospheric Research [Lauder]
20 CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA DIVISION OF BIOLOGY USA
21 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
22 Earth Observation Research Center
23 University of Toronto - Department of physics
24 KIT - Karlsruhe Institute of Technology
25 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres

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, these data have 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 these data in order to highlight how this latest version may be used in the future. We describe in detail how the data are 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 with 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 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. These data are available at https://doi.org/10.5285/18ef8247f52a4cb6a14013f8235cc1eb (Parker and Boesch, 2020).

Domaines: Océan, Atmosphère; Physique [physics]; Astrophysique [astro-ph]

Robert J. Parker, Alex J. Webb, Hartmut Boesch, Peter Somkuti, Rocio Barrio Guillo, et al.. A decade of GOSAT Proxy satellite CH4 observations. Earth System Science Data, 2020, 12 (4), pp.3383-3412. ⟨10.5194/essd-12-3383-2020⟩. ⟨hal-03109132⟩