The Greenhouse Gas Climate Change Initiative (GHG-CCI): Comparison and quality assessment of near-surface-sensitive satellite-derived CO2 and CH4 global data sets

Research output: Contribution to journalArticle

Abstract

The GHG-CCI project is one of several projects of the European Space Agency's (ESA) Climate Change Initiative (CCI). The goal of the CCI is to generate and deliver data sets of various satellite-derived Essential Climate Variables (ECVs) in line with GCOS (Global Climate Observing System) requirements. The "ECV Greenhouse Gases" (ECV GHG) is the global distribution of important climate relevant gases - atmospheric CO2 and CH4 - with a quality sufficient to obtain information on regional CO2 and CH4 sources and sinks. Two satellite instruments deliver the main input data for GHG-CCI: SCIAMACHY/ENVISAT and TANSO-FTS/GOSAT. The first order priority goal of GHG-CCI is the further development of retrieval algorithms for near-surface-sensitive column-averaged dry air mole fractions of CO2 and CH4, denoted XCO2 and XCH4, to meet the demanding user requirements. GHG-CCI focuses on four core data products: XCO2 from SCIAMACHY and TANSO and XCH4 from the same two sensors. For each of the four core data products at least two candidate retrieval algorithms have been independently further developed and the corresponding data products have been quality-assessed and inter-compared. This activity is referred to as "Round Robin" (RR) activity within the CCI. The main goal of the RR was to identify for each of the four core products which algorithms should be used to generate the Climate Research Data Package (CRDP). The CRDP will essentially be the first version of the ECV GHG. This manuscript gives an overview of the GHG-CCI RR and related activities. This comprises the establishment of the user requirements, the improvement of the candidate retrieval algorithms and comparisons with ground-based observations and models. The manuscript summarizes the final RR algorithm selection decision and its justification. Comparison with ground-based Total Carbon Column Observing Network (TCCON) data indicates that the "breakthrough" single measurement precision requirement has been met for SCIAMACHY and TANSO XCO2 (<3ppm) and TANSO XCH4 (<17ppb). The achieved relative accuracy for XCH4 is 3-15ppb for SCIAMACHY and 2-8ppb for TANSO depending on algorithm and time period. Meeting the 0.5ppm systematic error requirement for XCO2 remains a challenge: approximately 1ppm has been achieved at the validation sites but also larger differences have been found in regions remote from TCCON. More research is needed to identify the causes for the observed differences. In this context GHG-CCI suggests taking advantage of the ensemble of existing data products, for example, via the EnseMble Median Algorithm (EMMA).

Details

Authors
  • M. Buchwitz
  • M. Reuter
  • O. Schneising
  • H. Boesch
  • S. Guerlet
  • B. Dils
  • I. Aben
  • R. Armante
  • P. Bergamaschi
  • T. Blumenstock
  • H. Bovensmann
  • D. Brunner
  • B. Buchmann
  • J. P. Burrows
  • A. Butz
  • A. Chédin
  • F. Chevallier
  • C. D. Crevoisier
  • N. M. Deutscher
  • C. Frankenberg
  • F. Hase
  • O. P. Hasekamp
  • J. Heymann
  • T. Kaminski
  • A. Laeng
  • G. Lichtenberg
  • M. De Mazière
  • S. Noël
  • J. Notholt
  • J. Orphal
  • C. Popp
  • R. Parker
  • R. Sussmann
  • G. P. Stiller
  • T. Warneke
  • C. Zehner
  • A. Bril
  • D. Crisp
  • D. W.T. Griffith
  • A. Kuze
  • C. O'Dell
  • S. Oshchepkov
  • V. Sherlock
  • H. Suto
  • P. Wennberg
  • D. Wunch
  • T. Yokota
  • Y. Yoshida
External organisations
  • European Commission Joint Research Centre, Ispra
  • Laboratoire des Sciences du Climat et de l'Environnement
  • Karlsruhe Institute of Technology
  • University of Bremen
  • Belgian Institute for Space Aeronomy
  • Laboratoire de Meteorologie Dynamique
  • German Aerospace Center (DLR)
  • University of Bristol
  • European Space Agency - ESA
  • National Institute for Environmental Studies
  • Japan Aerospace Exploration Agency
  • University of Leicester
  • National Instiute for Space Research
  • Fastopt GmbH
  • Swiss Federal Laboratories for Materials Science and Technology
  • National Institute of Water and Atmospheric Research, New Zealand
  • California Institute of Technology
  • University of Wollongong
  • Colorado State University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Climate Research
  • Meteorology and Atmospheric Sciences

Keywords

  • Carbon dioxide, Climate change, GOSAT, Greenhouse gases, Methane, SCIAMACHY
Original languageEnglish
Pages (from-to)344-362
Number of pages19
JournalRemote Sensing of Environment
Volume162
Publication statusPublished - 2015 Jun 1
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes