08 Nov 2022
08 Nov 2022
Status: this preprint is currently under review for the journal AMT.

Update on the GOSAT TANSO–FTS SWIR Level 2 retrieval algorithm

Yu Someya1, Yukio Yoshida1, Hirofumi Ohyama1, Shohei Nomura1, Akihide Kamei1, Isamu Morino1, Hitoshi Mukai2, Tsuneo Matsunaga1, Joshua L. Laughner3, Voltaire A. Velazco4,5, Benedikt Herkommer6, Yao Té7, Mahesh Kumar Sha8, Rigel Kivi9, Minqiang Zhou10, Young Suk Oh11, Nicholas M. Deutscher5, and David W. T. Griffith5 Yu Someya et al.
  • 1Earth System Division, National Institute for Environmental Studies, Tsukuba, Japan
  • 2Center for Climate Change Adaptation, National Institute for Environmental Studies, Tsukuba, Japan
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 4Deutscher Wetterdienst, Meteorological Observatory Hohenpeissenberg, 82383, Germany
  • 5Centre for Atmospheric Chemistry, School of Earth, Atmospheric and Life Sciences, University of Wollongong, NSW 2522, Australia
  • 6Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Germany
  • 7Laboratoire d'Études du Rayonnement et de la Matière en Astrophysique et Atmosphères (LERMA-IPSL), Sorbonne Université, CNRS, Observatoire de Paris, PSL Université, 75005 Paris, France
  • 8Royal Belgian Institute for Space Agency (BIRA-IASB), Brussels, Belgium
  • 9Space and Earth Observation Centre, Finnish Meteorological Institute, Tähteläntie 62, 99600 Sodankylä, Finland
  • 10CNRC & LAGEO, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
  • 11National Institute of Meteorological Sciences, 33, Seohbuk-ro, Seogwipo-si, Jeju-do, 63568, Republic of Korea

Abstract. The National Institute for Environmental Studies has provided the column-averaged dry-air mole fraction of carbon dioxide and methane (XCO2 and XCH4) products (L2 products) obtained from the Greenhouse gases Observing SATellite for more than a decade. Recently, we updated the retrieval algorithm used to produce the new L2 product, V03.00. The main changes from the previous version (V02) of the retrieval algorithm are the treatment of cirrus clouds, the degradation model of the Thermal And Near-infrared Spectrometer for carbon Observation – Fourier Transform Spectrometer (TANSO-FTS), solar irradiance spectra, and gas absorption coefficient tables. The retrieval results from the updated algorithm showed improvements in fitting accuracies in the O2 A, weak CO2, and CH4 bands of TANSO-FTS, although the residuals increase in the strong CO2 band over the ocean. The direct comparison of the new product obtained from the updated (V03) algorithm with the previous version V02.90/91 and the validations using the Total Carbon Column Observing Network revealed that the V03 algorithm increases the amount of data without diminishing the data qualities of XCO2 and XCH4 over land. Further, the negative bias of XCO2 is larger than that of the previous version over the ocean, and bias correction is still necessary. Additionally, the V03 algorithm resolves the underestimation of the XCO2 growth rate compared with the in situ measurements over the ocean recently found using V02.90/91 and V02.95/96.

Yu Someya et al.

Status: open (until 13 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-281', Anonymous Referee #1, 26 Nov 2022 reply
  • RC2: 'Comment on amt-2022-281', T. E. Taylor, 29 Nov 2022 reply

Yu Someya et al.


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Short summary
This study presents an update of the NIES retrieval algorithm for the SWIR Level 2 product of GOSAT. The main changes in the algorithm from the previous version are the treatment of cirrus clouds, the degradation model of the sensor, solar irradiance, and gas absorption coefficient tables. The retrieval results showed improvements in fitting accuracy and an increase in the data amount over land. On the other hand, there are still large biases of XCO2 which should be corrected over the ocean.