1302.0700 (S Douté)
S Douté
This article presents a monitoring of the atmospheric dust in the south polar region during spring of martian year 27. Our goal is to contribute to identifying the source regions and to understanding lifting as well as transport mechanisms in relation with the seasonal ice regression and the dynamics of the atmosphere. This is of paramount importance since local dust storms generated in this region sometimes grow to global proportions. The imaging spectrometer OMEGA on board Mars Express has acquired the most comprehensive set of observations to date in the near-infrared (0.93-5.1 microns) of the southern high latitudes of Mars from mid-winter solstice (Ls=110, December 2004) to the end of the recession at Ls=320 (November 2005) . We use an original method presented in the companion paper in order to retrieve the optical depth of the atmospheric dust above mineral surfaces at a reference wavelength of one micron. The method is applied on a time series of OMEGA images acquired between Ls=220 and Ls=280 in conjunction with a complementary treatment of the seasonal cap. As a result the aerosol optical depth (AOD) is mapped and binned at a spatial resolution of 1.0.pixel-1 and with a mean period of AOD sampling ranging from less than two sols for latitudes higher than 80S to approximately six sols at latitudes in the interval 65-75S. We then generate and interpret time series of orthographic mosaics depicting the spatio-temporal distribution of the seasonal mean values, the variance and the local time dependence of the AOD. We conclude that two mechanisms play a major role for lifting and transporting efficiently mineral particles and create dust events or storms: (i) nighttime katabatic winds at locations where a favourable combination of frozen terrains and topography exists (ii) daytime mesoscale thermal winds at the edge of the cap when the defrosting area is sufficiently narrow.
View original:
http://arxiv.org/abs/1302.0700
No comments:
Post a Comment