The radiative impact of water ice clouds from a reanalysis of Mars Climate Sounder data

The radiative impact of water ice clouds on the atmosphere of Mars is analyzed via a reanalysis of Mars Climate Sounder (MCS) temperature and ice opacity profiles. Polar hood clouds only have a small radiative impact, while tropical clouds increase diurnally averaged temperatures at the 10 Pa level by similar to 10-15 K. Cloud radiative heating strengthens the meridional overturning circulation, increasing temperatures in the polar warmings by similar to 6-8 K and temperatures in the tropics by similar to 2 K (due to increased dust mass). The positions and wind speeds of the tropical and high-latitude jets are also modified through changes to the meridional temperature gradients. An effective ice particle radius of r(eff) = 1.4 mu m produces temperatures around the aphelion cloud belt in close agreement to MCS temperature retrievals. For high-altitude tropical clouds during northern autumn, a better agreement is found using r(eff) = 0.8 mu m.