Articles | Volume 6, issue 6
Atmos. Meas. Tech., 6, 1533–1547, 2013
Atmos. Meas. Tech., 6, 1533–1547, 2013

Research article 07 Jun 2013

Research article | 07 Jun 2013

Improvement of the retrieval algorithm for GOSAT SWIR XCO2 and XCH4 and their validation using TCCON data

Y. Yoshida1, N. Kikuchi1, I. Morino1, O. Uchino1, S. Oshchepkov1, A. Bril1, T. Saeki1, N. Schutgens2,*, G. C. Toon3, D. Wunch4, C. M. Roehl4, P. O. Wennberg4, D. W. T. Griffith5, N. M. Deutscher5,6, T. Warneke6, J. Notholt6, J. Robinson7, V. Sherlock7, B. Connor8, M. Rettinger9, R. Sussmann9, P. Ahonen10, P. Heikkinen10, E. Kyrö10, J. Mendonca11, K. Strong11, F. Hase12, S. Dohe12, and T. Yokota1 Y. Yoshida et al.
  • 1National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
  • 2Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8568, Japan
  • 3Jet Propulsion Laboratory, California Institute for Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109-8099, USA
  • 4California Institute for Technology, Pasadena, CA, 91125-2100, USA
  • 5Centre for Atmospheric Chemistry, University of Wollongong, New South Wales 2522, Australia
  • 6Institute of Environmental Physics, University of Bremen, 28334 Bremen, Germany
  • 7National Institute of Water and Atmospheric Research, Wellington, New Zealand
  • 8BC Consulting, Alexandra, New Zealand
  • 9IMK-IFU, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany
  • 10Finnish Meteorological Institute, Arctic Research, Sodankylä, Finland
  • 11Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 1A7, Canada
  • 12IMK-ASF, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • *now at: Atmosphere, Ocean, Planetary Physics sub-department, Clarendon Laboratory, Oxford University, Oxford, UK

Abstract. The column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) have been retrieved from Greenhouse gases Observing SATellite (GOSAT) Short-Wavelength InfraRed (SWIR) observations and released as a SWIR L2 product from the National Institute for Environmental Studies (NIES). XCO2 and XCH4 retrieved using the version 01.xx retrieval algorithm showed large negative biases and standard deviations (−8.85 and 4.75 ppm for XCO2 and −20.4 and 18.9 ppb for XCH4, respectively) compared with data of the Total Carbon Column Observing Network (TCCON). Multiple reasons for these error characteristics (e.g., solar irradiance database, handling of aerosol scattering) are identified and corrected in a revised version of the retrieval algorithm (version 02.xx). The improved retrieval algorithm shows much smaller biases and standard deviations (−1.48 and 2.09 ppm for XCO2 and −5.9 and 12.6 ppb for XCH4, respectively) than the version 01.xx. Also, the number of post-screened measurements is increased, especially at northern mid- and high-latitudinal areas.