Temperature–pressure profile taken from Hue et al. (2018; black solid line). Eddy diffusion coefficient K_zz profile from Moses et al. (2005; red solid line – Model A) compared to our nominal profile (blue solid line – Model B). The CH₄ homopause occurs where the K_zz profile crosses the CH₄ molecular diffusion coefficient profile (blue dashed lines). The K_zz value derived by Greathouse et al. (2010) at this level is shown for comparison. Our nominal K_zz is unconstrained from our H₂O observationsfor pressures higher than ~5 mbar.