Assess the realism of the thin CO2 emitting layer under vertical mixing

Determine whether CO2 emission realistically traces a thin surface layer above the H2O reservoir when efficient vertical mixing may rapidly spread the CO2 throughout the disk, by incorporating vertical mixing into models of CO2 emission and abundance structure.

Background

The models produce CO2 emission predominantly from a thin surface layer in which the H2O column is insufficient for self-shielding. This layer controls the inferred CO2 column and causes the CO2/H2O ratio to behave differently from predictions based on vertically constant abundances.

The paper does not include vertical mixing in this treatment. Because efficient vertical mixing could redistribute CO2 away from the thin emitting layer and alter both its abundance structure and observable isotopologue emission, the physical realism of interpreting the CO2 emission as originating from that layer remains unresolved.