MARCI-Observed Wave-2 Water Ice Clouds
The polar hoods on Mars are thick fogs of water ice crystals that can be as deep as 10 km. These hoods form during fall and winter in each hemisphere, but have a distinct wavenumber-2, longitudinal pattern in the northern hemisphere that is present year after year (Figure 1). The persistence of this pattern suggests the presence of a planetary stationary wave. Using the NASA/Ames Legacy GCM to study this feature, we find that a stationary wavenumber-2 field forced by surface topography does produce a polar hood that looks very much like the observed feature. The results of this study have been published in Icarus.
Figure 1: Latitude vs longitude plots of the ultraviolet (UV) column opacities from four different Mars Years (MY). The opacities are derived from the Mars Color Imager on the Mars Reconnaissance Observer spacecraft. UV observations are very sensitive to presence water ice clouds. Notice the wave like longitudinal structure of the polar hood. From Haberle et al. (2020).