Molecular ratio n(CO)/n(H₂O). Top: 1D structures of the n(CO)/n(H₂O) distribution on HAT-P-7b. We follow the same colour code like in Fig. 3: blue – nightside, orange – dayside; day-night terminator: light blue and light orange, black-dashed: sub-stellar and anti-stellar points. Middle: global n(CO)/n(H₂O) map at p_gas = 10⁻³ bar representing the possibly optically thin part of the atmosphere. Bottom: global n(CO)/n(H₂O) map at p_gas = 10⁻²bar showing the transitional region from warm to cold (Fig. 3). The black contour lines in the 2D maps show where n(CO) = n(H₂O). As seen in 1D plot (top) for p_gas >10 mbar, only 2 profiles have n(CO) < n(H₂O) on the “far” nightside.