Structure of WASP-121b at the substellar point. We plot the pressure–temperature profile (black line) together with elemental abundances (dashed lines). Contribution functions at 1.25 μm (blue) and 1.4 μm (red) are plotted on the left side of the plot for the fiducial model (solid line), the model post processed without H⁻ opacities (long dashed line) and the model post processed with a constant water abundance (dotted line). Contribution functions have been normalized to go from zero to one and scaled to improve visibility.