Cloud formation under Mars Pathfinder conditions

Water ice cloud formation on Mars is more difficult than presumed: Laboratory studies of ice nucleation on surrogate materials

“…6. A particular distribution of particle sizes (solid curve) with a maximum near 3 lm results when clouds are nucleated in the NASA Ames Mars GCM cloud model (Colaprete and Toon, 2000;Colaprete et al, 1999) at a constant value of m = 0.95. In contrast, when the contact parameter mimics the temperature dependence seen in the lab for ice nucleation on Arizona Test Dust, the size distribution is broader (dashed curve) and shifts to larger sizes.…”

“…6. Particle mass distribution (dM/dr) calculated from the same point (in both space and time) from simulations using a NASA Ames Mars GCM cloud model (Colaprete and Toon, 2000;Colaprete et al, 1999) for two runs for which only the contact parameter, m, was changed. In the first (solid curve), m = 0.95, and in the second (dashed), the contact parameter was described as a function of temperature, as derived from the laboratory measurements in this study.…”

“…Currently some general circulation models (GCMs) do address the microphysics of clouds (Montmessin et al, 2004;Colaprete et al, 2008), commonly using a contact parameter of m = 0.95, which would correlate to a critical saturation for cloud onset of S crit = 1.3 for a planar substrate when T = 185 K, where the saturation ratio, S, is defined as the ratio of the water partial pressure to the equilibrium vapor pressure for hexagonal ice at the given temperature. While these microphysical treatments have had some success in reproducing the gross seasonal characteristics of the martian water cycle, their sensitivity to the predicted cloud properties, such as particle size, has been demonstrated (Richardson et al, 2002;Colaprete et al, 1999;Montmessin et al, 2004). Uncertainties in surface boundary conditions, and a lack of data on cloud processes under martian conditions, make it difficult to determine if the success of these models is the result of accurate physical representation or the result of offsetting errors.…”

The Radiative Effects of Martian Water Ice Clouds on the Local Atmospheric Temperature Profile

“…The cloud microphysical model includes the three processes particle nucleation, condensation, and sedimentation (Colaprete et al 1999, Michelangeli et al 1993, Toon et al 1988. This model treats dust as condensation nuclei (CN) and allows for the formation and evolution of water ice clouds.…”

Mars: a small terrestrial planet

“…Montmessin et al (2004) also obtained a good agreement with the data, and analyzed in more detail the influence of water ice clouds. Following analyses by Haberle et al (1999) and Colaprete et al (1999), new models (Hinson and Wilson 2004;Madeleine et al 2012) have considered the radiative effect of these clouds, which in some cases can generate temperature inversions. A further improved 3D GCM model has been developed by Navarro et al (2014), including the nucleation on dust particles, ice particle growth in a supersaturated atmosphere, and scavenging of dust particles due to ice condensation.…”