CH₄ (J = 6 − 5) spectrum toward Jupiter’s center from upGreat (black line) and HIFI (gray-shaded). The velocity scale refers to the Jovian system barycenter. The continuous lines refer to the synthetic spectra (with and without pressure-shift, in orange, respectively green). The dark-blue line profile is for a sightline bounded by the tropopause (p = 145 mbar in this model) and does not show the stratospheric contribution.