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|Title:||CH<inf>4</inf> concentrations over the Amazon from GOSAT consistent with in situ vertical profile data|
|Authors:||Webb, Alex J.|
Parker, Robert J.
Gatti, L. V.
Palmer, P. I.
Basso, L. S.
Chipperfield, M. P.
Correia, C. S. C.
Domingues, L. G.
Miller, J. B.
|Publisher:||American Geophysical Union (AGU), Wiley|
|Citation:||Journal of Geophysical Research: Atmospheres, 2016, 121, 11,006–11,020|
|Abstract:||The Amazon Basin contains large wetland ecosystems which are important sources of methane (CH4). Spaceborne observations of atmospheric CH4 can provide constraints on emissions from these remote ecosystems, but lack of validation precludes robust estimates. We present the first validation of CH4 columns in the Amazon from the Greenhouse gases Observing SATellite (GOSAT) using aircraft measurements of CH4 over five sites across the Amazon Basin. These aircraft profiles, combined with stratospheric results from the TOMCAT chemical transport model, are vertically integrated allowing direct comparison to the GOSAT XCH4 measurements (the column-averaged dry air mole fraction of CH4). The measurements agree within uncertainties or show no significant difference at three of the aircraft sites, with differences ranging from -1.9 ppb to 6.6 ppb, while at two sites GOSAT XCH4 is shown to be slightly higher than aircraft measurements, by 8.1 ppb and 9.7 ppb. The seasonality in XCH4 seen by the aircraft profiles is also well captured (correlation coefficients from 0.61 to 0.90). GOSAT observes elevated concentrations in the northwest corner of South America in the dry season and enhanced concentrations elsewhere in the Amazon Basin in the wet season, with the strongest seasonal differences coinciding with regions in Bolivia known to contain large wetlands. Our results are encouraging evidence that these GOSAT CH4 columns are generally in good agreement with in situ measurements, and understanding the magnitude of any remaining biases between the two will allow more confidence in the application of XCH4 to constrain Amazonian CH4 fluxes.|
|Rights:||©2016. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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