  The middle infrared (MIR) channel of the Atmospheric Chemistry Suite (ACS)
instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission
has performed Solar occultation measurements of the Martian atmosphere in the
2.3-4.2 $\mu$m spectral range since March 2018, which now covers two Martian
Years (MY). We use the methodology previously developed for the study of the MY
34 Global Dust Storm (GDS) (Stcherbinine et al., 2020) to monitor the
properties (effective radii, extinction, altitude) of the Martian water ice
clouds over the first two Martian years covered by ACS-MIR. The observations
encompass the period $L_s$ = 163{\deg} in MY 34 to $L_s$ = 181{\deg} in MY 36.
We determine that the typical altitude of the clouds varies by 20 to 40 km
between the summer and winter, with a maximum extension up to 80 km during
summer in the midlatitudes. Similarly, we also note that for a limited temporal
range, the altitude of the clouds also varies by 20 to 40 km between the polar
regions and the midlatitudes. We also compare observations acquired during the
MY 34 GDS to observations from the same period in MY 35, using that latter as a
reference to characterize the effects of this GDS on the clouds' properties. In
addition, we compare our retrievals with the predictions of the Mars Planetary
Climate Model (PCM), which shows a reasonable agreement overall for the
altitude of the clouds, although the model usually predicts lower altitudes for
the top of the clouds.
