Near-Surface Boundary Layer

Near-Surface Boundary Layer

Five temperature profiles from latitudes between 30 deg S and 64 deg S during early summer in the southern hemisphere (Ls = 275-303 deg) are shown in the figure above. Only the lower portion of each profile is shown to emphasize structure near the surface. The local time varies from 18:40 (evening) through midnight to 03:53 (predawn). Measurements at 21:16 and 23:21 are just before and after sunset, respectively. The dashed line shows the adiabatic temperature gradient. This is the rate at which a warm parcel of the martian atmosphere cools as it rises and expands.

The profiles resolve the nighttime radiative temperature inversion that develops near the surface. At altitudes below about 3 km, the temperature gradient varies from slightly subadiabatic in the evening to a strong inversion before sunrise. The temperature near the surface decreases by about 40 K during this time interval, comparable to the variations measured at the surface by the Viking landers and Mars Pathfinder. The profile at 18:40 suggests that daytime convection extends to an altitude of 8-10 km during summer. These variations in thermal structure are driven by daytime heating and nighttime cooling of the surface.

Moving from left to right near the surface, the measurement locations and the Planetary Data System (PDS) file names for these profiles are:

Latitude Longitude Solar Longitude (Ls) TPS File Name
30 deg S 21 deg E 275 deg 8045P37A.TPS
60 deg S 272 deg E 285 deg 8061G22A.TPS
64 deg S 342 deg E 288 deg 8067D3JA.TPS
61 deg S 118 deg E 293 deg 8073U56A.TPS
34 deg S 234 deg E 303 deg 8091W23A.TPS

The atmospheric temperature-pressure profile data files shown in the table may be accessed here, along with all of the other profiles which have been permanently archived with PDS by the MGS Radio Science Team.


Last updated: November 17, 1999
Dave Hinson / Joe Twicken