Effects of atmospheric light scattering on spectroscopic observations of greenhouse gases from space: Validation of PPDF-based CO2 retrievals from GOSAT

Sergey Oshchepkov, Andrey Bril, Tatsuya Yokota, Isamu Morino, Yukio Yoshida, Tsuneo Matsunaga, Dmitry Belikov, Debra Wunch, Paul Wennberg, Geoffrey Toon, Christopher O'Dell, André Butz, Sandrine Guerlet, Austin Cogan, Hartmut Boesch, Nawo Eguchi, Nicholas Deutscher, David Griffith, Ronald MacAtangay, Justus NotholtRalf Sussmann, Markus Rettinger, Vanessa Sherlock, John Robinson, Esko Kyrö, Pauli Heikkinen, Dietrich G. Feist, Tomoo Nagahama, Nikolay Kadygrov, Shamil Maksyutov, Osamu Uchino, Hiroshi Watanabe

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Abstract

This report describes a validation study of Greenhouse gases Observing Satellite (GOSAT) data processing using ground-based measurements of the Total Carbon Column Observing Network (TCCON) as reference data for column-averaged dry air mole fractions of atmospheric carbon dioxide (XCO2). We applied the photon path length probability density function method to validate XCO2 retrievals from GOSAT data obtained during 22months starting from June 2009. This method permitted direct evaluation of optical path modifications due to atmospheric light scattering that would have a negligible impact on ground-based TCCON measurements but could significantly affect gas retrievals when observing reflected sunlight from space. Our results reveal effects of optical path lengthening over Northern Hemispheric stations, essentially from May-September of each year, and of optical path shortening for sun-glint observations in tropical regions. These effects are supported by seasonal trends in aerosol optical depth derived from an offline three-dimensional aerosol transport model and by cirrus optical depth derived from space-based measurements of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument. Removal of observations that were highly contaminated by aerosol and cloud from the GOSAT data set resulted in acceptable agreement in the seasonal variability of XCO2 over each station as compared with TCCON measurements. Statistical comparisons between GOSAT and TCCON coincident measurements of CO2 column abundance show a correlation coefficient of 0.85, standard deviation of 1.80ppm, and a sub-ppm negative bias of -0.43ppm for all TCCON stations. Global distributions of monthly mean retrieved XCO2 with a spatial resolution of 2.5° latitude×2.5° longitude show agreement within∼2.5°ppm with those predicted by the atmospheric tracer transport model.

Original languageEnglish
Article numberD12305
JournalJournal of Geophysical Research Atmospheres
Volume117
Issue number12
DOIs
Publication statusPublished - Jan 1 2012

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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    Oshchepkov, S., Bril, A., Yokota, T., Morino, I., Yoshida, Y., Matsunaga, T., Belikov, D., Wunch, D., Wennberg, P., Toon, G., O'Dell, C., Butz, A., Guerlet, S., Cogan, A., Boesch, H., Eguchi, N., Deutscher, N., Griffith, D., MacAtangay, R., ... Watanabe, H. (2012). Effects of atmospheric light scattering on spectroscopic observations of greenhouse gases from space: Validation of PPDF-based CO2 retrievals from GOSAT. Journal of Geophysical Research Atmospheres, 117(12), [D12305]. https://doi.org/10.1029/2012JD017505