Figure 3.

Temperature pressure profiles measured by radio occultation in Uranus (green) and Neptune (blue) extended in the deep atmosphere following wet adiabats with different abundances of condensables. Stars in a show the bottom pressure layer sensed in radio occultation experiments performed by Voyager 2 in Uranus (green) and Neptune (blue). (a and b): Dashed horizontal lines represent the cloud base level for different condensates and abundances. Red profiles indicate possible thermal profiles in the case that moist convection is fully inhibited producing sharp discontinuities in temperature. These discontinuities would be found at critical abundances of methane and water but for simplicity only the one from high water abundance is shown based in [15]. (c) Density profiles as a function of altitude above the 1 bar level except for the convectively inhibited profile. The kink in the 80 times solar abundance profile at 550 km is caused by the critical point of water at 647 K. Pink dotted lines in b and c show the extrapolation of Neptune’s thermal profile following an adiabat without latent heat release but considering volatiles with a deep abundance of 80 times solar and relative humidities of 99%. (Online version in colour.)