Comparison of measured isotopic profiles of CO from TGO solar occultation observations with model results. The left, middle, and right panels show vertical profiles of ¹⁸O/¹⁶O in CO, ¹³C/¹²C in CO, and ¹³C¹⁶O/¹²C¹⁸O, respectively. The isotopic ratios are normalized to the standard reference values of VSMOW (¹⁸O/¹⁶O = 2.0052 × 10⁻³) and Vienna Pee Dee Belemnite (VPDB; ¹³C/¹²C = 1.123 × 10⁻²). The blue lines represent the calculation results: the solid, dashed, and dotted lines correspond to the results with the standard eddy diffusion coefficient, a coefficient one order of magnitude smaller, and a coefficient one order of magnitude larger, respectively. The red and orange bars represent the values retrieved from TGO solar occultation measurements by J. Alday et al. (2023) and S. Aoki et al. (2023), respectively.