Sing et al. (2008a,b) used observations of the Na D line profile to constrain the temperature profile in the upper atmosphere. They suggested that Na condenses into clouds near the 3 mbar level, and thus predicted a deep minimum in temperature in this region that is required for condensation. The detection of Si2+ implies that condensation of Na in the lower atmosphere is unlikely (Paper II), and thus this result is unreliable. Relying on the same observations, Vidal-Madjar et al. (2011a,b) predicted that the temperature increases steeply from 1300 K to 3500 K near the 1 μbar level. However, their method to retrieve the temperature relies on the density scale height of Na to express the optical depth along the line of sight (LOS). This is not consistent with the argument that Na is depleted above the 3 mbar level. If such a depletion takes place, the density scale height of Na is not the same as the scale height of the atmosphere and it cannot be used to retrieve temperatures.
upper atmosphere
level
3 mbar
mbar
upper atmosphere
temperature
1300 K to 3500 K
K
upper atmosphere
level
1 μbar
μbar
upper atmosphere
level
3 mbar
mbar