MGS radio occultation measurements of temperature versus pressure and longitude. Pressure is given in pascals, with 100 Pa = 1 mb. The contour interval is 2 K. The season is midwinter in the southern hemisphere (Ls = 148-162 deg). The line near the bottom of the figure indicates the pressure at the surface, which has an average value of 430 Pa.
The figure was constructed from 25 days of measurements (175 vertical profiles) spread evenly in longitude near 67 deg S latitude. The data have been averaged to isolate the components of the temperature field that remain stationary with respect to the surface. Temperatures range from a minimum of 139 K to a maximum of 161 K. The temperature field contains roughly equal contributions at zonal wave numbers 1 and 2 (i.e., 1 and 2 cycles per 360 deg of longitude, respectively). This thermal structure is associated with stationary Rossby waves. These low-frequency, planetary-scale oscillations are a prominent feature of the winter weather on Mars. Mars Global Surveyor is providing the first detailed measurements of their spatial structure and seasonal evolution.