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Remote sensing of near-infrared chlorophyll fluorescence from space in scattering atmospheres: implications for its retrieval and interferences with atmospheric CO_2 retrievals

Frankenberg, C. and O’Dell, C. and Guanter, L. and McDuffie, J. (2012) Remote sensing of near-infrared chlorophyll fluorescence from space in scattering atmospheres: implications for its retrieval and interferences with atmospheric CO_2 retrievals. Atmospheric Measurement Techniques, 5 (8). pp. 2081-2094. ISSN 1867-1381. https://resolver.caltech.edu/CaltechAUTHORS:20150508-090326387

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Abstract

With the advent of dedicated greenhouse gas space-borne spectrometers sporting high resolution spectra in the O_2 A-band spectral region (755–774 nm), the retrieval of chlorophyll fluorescence has become feasible on a global scale. If unaccounted for, however, fluorescence can indirectly perturb the greenhouse gas retrievals as it perturbs the oxygen absorption features. As atmospheric CO_2 measurements are used to invert net fluxes at the land–atmosphere interface, a bias caused by fluorescence can be crucial as it will spatially correlate with the fluxes to be inverted. Avoiding a bias and retrieving fluorescence accurately will provide additional constraints on both the net and gross fluxes in the global carbon cycle. We show that chlorophyll fluorescence, if neglected, systematically interferes with full-physics multi-band X_(CO_2) retrievals using the O_2 A-band. Systematic biases in X_(CO_2) can amount to +1 ppm if fluorescence constitutes 1% to the continuum level radiance. We show that this bias can be largely eliminated by simultaneously fitting fluorescence in a full-physics based retrieval. If fluorescence is the primary target, a dedicated but very simple retrieval based purely on Fraunhofer lines is shown to be more accurate and very robust even in the presence of large scattering optical depths. We find that about 80% of the surface fluorescence is retained at the top-of-atmosphere, even for cloud optical thicknesses around 2–5. We further show that small instrument modifications to future O_2 A-band spectrometer spectral ranges can result in largely reduced random errors in chlorophyll fluorescence, paving the way towards a more dedicated instrument exploiting solar absorption features only.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.5194/amt-5-2081-2012 DOIArticle
http://www.atmos-meas-tech.net/5/2081/2012/amt-5-2081-2012.htmlPublisherArticle
ORCID:
AuthorORCID
Frankenberg, C.0000-0002-0546-5857
O’Dell, C.0000-0002-0271-8433
Guanter, L.0000-0002-8389-5764
Additional Information:© 2012 Author(s). CC Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 24 February 2012 – Published in Atmos. Meas. Tech. Discuss.: 29 March 2012. Revised: 12 June 2012 – Accepted: 20 July 2012 – Published: 28 August 2012. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Government Sponsorship acknowledged. We appreciate the intense discussions at AMTD, which helped improve our manuscript.
Group:Keck Institute for Space Studies
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20150508-090326387
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150508-090326387
Official Citation:Frankenberg, C., O'Dell, C., Guanter, L., and McDuffie, J.: Remote sensing of near-infrared chlorophyll fluorescence from space in scattering atmospheres: implications for its retrieval and interferences with atmospheric CO2 retrievals, Atmos. Meas. Tech., 5, 2081-2094, doi:10.5194/amt-5-2081-2012, 2012
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57367
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 May 2015 16:24
Last Modified:11 Oct 2019 21:17

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