Satellite-derived cloud motion winds in the north polar region of Mars

Much of what we know about the global atmospheric circulation of Mars has come from numerical models as direct observations of the winds are scarce. The thermal structure has been used to derive the zonal average patterns which are reproduced well by the different circulation models. Cloud tracking techniques have been used to study the atmospheric circulations of Venus and the Jovian planets, but have not been used widely for Mars due to the lack of overlapping imaging observations over a short time interval. The Mars Orbiter Camera (MOC) on Mars Global Surveyor (MGS) provided the first overlapping images in the polar regions from consecutive passes, suitable for tracking clouds. Wang and Ingersoll used such images to measure cloud-tracked winds by a visual tracking method.

The Mars Reconnaissance Orbiter (MRO) currently orbiting Mars is returning higher resolution global images of Mars on each orbit, providing good overlap poleward of 50° latitude from orbit to orbit (approximately every two hours), enabling the use of a digital tracking method for cloud tracking. The Mars Color Imager (MARCI) on the MRO provides 1 km resolution image data (at nadir) in 7 color bands. This resolution is much improved over the two-filter, 7.5 km data from the MOC on MGS.

The spatial and temporal resolution of the MARCI images are similar to the Earth-based polar weather satellite data, therefore we will use our proven automated digital winds derivation technique for tracking cloud features. A description of the data, cloud tracking method, and early results will be presented.