Methane mixing ratio and saturation mixing ratio profiles in the atmospheres of Uranus and Neptune. For Uranus’ atmosphere, the temperature and mole fraction profiles are the same as those used by Irwin et al. (2018, 2022), which are based on the ’F1’ temperature profile determined by Sromovsky et al. (2011). For Neptune, the temperature and mole fraction profiles are the same as those used in Irwin et al. (2019a, 2021), which are based on the ’N’ profile determined by Lindal (1992). The horizontal blue dashed lines indicate the pressures where Lindal et al. (1987) (L87) and Lindal (1992) (L92) reported changes in the atmospheric refractivity. The methane saturation profiles are computed using the expressions given in Fray & Schmitt (2009).