Abstract
Background: Mars si both a windy and dusty environment. Ariborne dust is a crucial climate component on Mars. It impacts atmospheric circulations at large-, meso- and micro-scales, which in turn control dust lifting from the surface and transport in the atmosphere. Dust lifting processes and feedbacks on atmospheric circulations are currently not well understood. Method: Our purpose is to show how mesoscale models and large-eddy simulations help to explore small-scale circulation patterns which are potentially important for lifting dust into the atmosphere but which are unresolved by global climate models. We focus on variations of friction velocity, u *, relevant for dust lifting, in particular investigating maximum values and the spatial and temporal variability of u *. Conclusion: Meteorological scales between 100 km and 10 km can be studied by high-resolution global circulation and limited-area mesoscale models, which both show strong topographic control of the daytime and nighttime near-surface winds. Scales below 10 km and 1 km are dominated by turbulent gusts and dust devils, two distinct convective boundary layer processes likely to lift dust from the surface. In low-latitude regions, boundary layer depth and friction velocity u * are correlated with surface altimetry. Further studies will be carried out to parameterize lifting by boundary layer processes and dust radiative effects once transported in the atmosphere.
Highlights
It is characterized by intense katabatic and anabatic winds, over craters, volcanoes, canyons (Rafkin et al, 2002; Tyler et al 2002; Toigo and Richardson 2003; Spiga and Forget 2009), thermal circulations induced by soil thermophysical heterogeneities (Toigo et al 2002; Kauhanen et al 2008), local dust storms (Rafkin 2009) and regionalscale transient eddies, mostly in polar regions (Tyler and Barnes 2005)
We focus on mesoscale and microscale variations of friction velocity u* relevant for dust lifting, in particular maximum values of u*
We have investigated meteorological scales between 100 km and 10 km using both the high-resolution UK global circulation models (GCMs) and the LMD mesoscale model with similar physical schemes
Summary
Meteorological scales b etween 1 00 k m a nd 10 km can b e s tudied b y hi gh-resolution global circulation and limited-area mesoscale models, which both show strong topographic control of the daytime and nighttime near-surface winds. Scales below 10 km and 1 km are dominated by turbulent g usts a nd d ust d evils, tw o d istinct c onvective b oundary l ayer processes l ikely to l ift d ust from the surface. In low-latitude regions, boundary layer depth and friction velocity u* are correlated with s urface a ltimetry. Further s tudies w ill b e c arried o ut to p arameterize l ifting b y b oundary l ayer processes and dust radiative effects once transported in the atmosphere
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