Journal
JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER
Volume 113, Issue 16, Pages 2009-2017Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jqsrt.2012.07.013
Keywords
Carbon dioxide; CO2; Isotopes; Isotopologues; Remote sensing; FTS; Satellite; GOSAT
Categories
Funding
- ESA/ESRIN (GHG-CCI)
- EU FP7 (MACC-II)
- DLR (SADOS)
- State and the University of Bremen
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Pressing open questions about the carbon cycle can be addressed with precise measurements of the three most abundant CO2 isotopologues (OCO)-O-16-C-12-O-16, (OCO)-O-16-C-13-O-16, and (OCO)-O-16-C-12-O-18. Such measurements can, e.g., help to further constrain oceanic and biospheric net fluxes or to differentiate between the gross biospheric fluxes photosynthesis and respiration. The 2041-2047 nm (about 4885-4900 cm(-1)) spectral region contains separated absorption lines of the three most abundant CO2 isotopologues. Their spectral properties make this spectral region well suited for the use of a light path proxy method for the retrieval of delta C-13 and delta O-18 (the ratio of heavier to lighter isotopologues relative to a standard). An optimal estimation based light path proxy retrieval for delta C-13 and delta O-18 has been set up, applicable to GOSAT (Greenhouse gases Observing Satellite) and ground-based FTS (Fourier transform spectrometer) measurements. Initial results show that it is possible to retrieve delta C-13 and delta O-18 from ground-based FTS instruments with a precision of 0.6-1.6 parts per thousand and from GOSAT with a precision of about 30 parts per thousand. Comparison of the achievable precision with the expected atmospheric signals shows that ground-based FTS remote sensing measurements have the potential to gain valuable information on delta C-13 and delta O-18 if averaging a sufficient number of measurements. It seems unlikely that this applies also to GOSAT because of the lower precision and a conceptual larger sensitivity to scattering related errors in satellite viewing geometry. (C) 2012 Elsevier Ltd. All rights reserved.
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