each channel to a perturbation in each of the parameters in [**x**]{}) for the synthetic data (Figure 3). The spectrum is most sensitive to perturbations in the opacities that govern the temperature profile. The 1.7 $\mu$m and 2.2 $\mu$m channels are most sensitive to changes in the temperature profile. This is because there aren’t large absorption features at these wavelengths, meaning, these channels are most sensitive to the flux from deeper layers (1-10 bars). This also partially explains why $\kappa_{IR}$ and $\kappa_{v1}$ have opposite responses. An increase in $\kappa_{IR}$ results in an increase in flux due to an increase in temperature in the deep layers probed by these channels, as can be seen in (19). An increase in $\kappa_{v1}$ results in a decrease of flux in these channels due to a decrease in temperature in the deeper layers. From (19) an increase in $\kappa_{v1}$ increases the temperature above the $\sim 0.1$bar level, and in order to maintain radiative equilibrium at the top of the atmosphere, a decrease in temperature in the deeper layers must occur, and also a higher $\kappa_{v}$ prevents the stellar flux from penetrating into the deeper atmosphere. The opposite is true near 2.9 $\mu$m which is more 