On the potential of the 2041–2047nm spectral region for remote sensing of atmospheric CO2 isotopologues

Abstract: Pressing open questions about the carbon cycle can be addressed with precise measurements of the three most abundant CO2 isotopologues 16O12C16O, 16O13C16O, and . 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 (about ) 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 and (the ratio of heavier to lighter isotopologues relative to a standard). An optimal estimation based light path proxy retrieval for and 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 and from ground-based FTS instruments with a precision of and from GOSAT with a precision of about . 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 and 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. [Copyright &y& Elsevier]