Fig. 2: Determination of δ18O-CO and δ13C-CO source signatures for CO originating from the photolysis of CO2.
From: Isotopic source signatures of stratospheric CO inferred from in situ vertical profiles
The estimated isotopic composition of CO source mixture derived from measured δ18O-CO and δ13C-CO and corrected for OH sink isotope fractionation vs. the inverse CO mole fraction for the 3 uppermost samples of the dataset above 20 km (pressure < 60 hPa) from April 26, September 4 and 6, 2017. Ordinary least squares regression was performed on the data. The error bars represent the measurement uncertainty of 3 ppb for the CO mole fractions on the axis, with uncertainty propagation used to derive the 1/y(CO) uncertainty. The uncertainty in the CO isotope composition was 0.5 per mil. Both of these uncertainties, in addition to the uncertainty due to the OH correction, are used to estimate the uncertainty in the source signature shown on the PDFs on the left.
