Total cross-correlation signal from only H₂O (panels a and d), only CO ( panels b and e), and H₂O + CO (panels c and f) for the atmosphere of WASP-20b, shown as a function of rest-frame velocity and planet-projected orbital velocity. 1D models were used in the top row, and 3D GCM models were in the bottom row. Both model types are cloud free, in chemical equilibrium, and without thermal inversion. They contain a VMR equal to −3.3 for H₂O and to −3.4 and -3.5 for CO in the 1D and 3D models, respectively.