Top: map of the line depth ratio of HDO/CO₂ retrieved from the TEXES data recorded on July 3, 2014 (Ls = 156°). The black circle corresponds to region B where the TEXES spectra were modeled (see text). Bottom left: TEXES map of the HDO/CO₂ mixing ratio inferred from the HDO/CO₂ line depth ratio. Bottom right: GCM synthetic map of the HDO mixing ratio (ppbv) calculated for the same observing conditions.