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Title: Effects of atmospheric light scattering on spectroscopic observations of greenhouse gases from space: Validation of PPDF-based CO retrievals from GOSAT
Authors: Oshchepkov, S.
Bril, A.
Yokota, T.
Morino, I.
Yoshida, Y.
Matsunaga, T.
Belikov, D.
Maksyutov, S.
Uchino, O.
Watanabe, H.
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.
Deutscher, N.
Notholt, J.
Sussmann, R.
Rettinger, M.
Sherlock, V.
Robinson, J.
Kyrö, E.
Heikkinen, P.
Feist, D. G.
Nagahama, T.
Kadygrov, N.
First Published: 23-Jun-2012
Publisher: American Geophysical Union (AGU); Wiley
Citation: Journal of Geophysical Research D: ATMOSPHERES, 2012, 117 (12)
Abstract: [1] 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 XCO2retrievals from GOSAT data obtained during 22 months 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 CO2column abundance show a correlation coefficient of 0.85, standard deviation of 1.80 ppm, and a sub-ppm negative bias of −0.43 ppm 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.
DOI Link: 10.1029/2012JD017505
ISSN: 0148-0227
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2012 by the American Geophysical Union. All rights reserved. Archived with reference to Usage Permissions granted to authors, available at
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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