On the infrared radiative properties of CO₂ ice clouds: Application to Mars

We have investigated the effect on the observed 20 µm brightness temperatures measured by the IRTM instrument, of the presence of cloud layers of CO 2 ice particles. The results show that such clouds have a profound effect, and a layer corresponding to visible thickness of ∼0.5, can create brightness temperatures of 120‐130K, even when the surface is at 150K. This suggests that these clouds may also contribute to the effect of brightness temperatures below the CO 2 frost point, which have been observed over the southern winter polar region. This article contains supplementary material.