The Mars Pathfinder (MPF) arrived on the Martian surface on 4 July
1997 to become only the third successful landed mission to Mars, recording
surface meteorological data intermittently over a period of 83 Martian days
("sols"). The in situ observations made by the MPF meteorology (MET) experiment
were recorded at much greater precision than those of the previous
missions, Viking Landers 1 and 2. These observations have been analyzed,
focusing primarily upon the four so-called "Presidential" sessions, which each
covered a complete diurnal cycle.
The signature of very strong convective activity was seen in the temperature
data, beginning soon after sunrise with temperatures changing as much
as 14.39 K over the four-second interval between observations, and ceasing in
late afternoon at the collapse of the boundary layer. Less extreme variability
occurred at most other times of day and night.
Examination of the first ten tidal pressure harmonic amplitudes for each
Presidential session revealed strong diurnal and semidiurnal amplitudes and
smaller, yet significant, amplitudes at the higher tidal frequencies. The normalized
diurnal amplitude was slightly more than 1.7% for one session and
averaged ~2.5% for the other three sessions. The semidiurnal amplitude averaged
~1.3%. A pattern in the tidal pressure harmonic amplitudes exists, in
which odd-numbered harmonics (excluding the diurnal frequency) have smaller
amplitudes than those of the next lower and next higher, even-numbered harmonics.
Wind direction data for one Presidential session show very high variability
throughout most of the diurnal cycle, the most intense activity occurring
during the daytime convective period. A generally clockwise rotation of the
mean wind direction was observed throughout the session.
Temperature and wind data were examined closely for evidence of contamination
of the temperature data by thermal effects of the lander itself. No
evidence was found for such "lander interference" in the morning, but lander
interference may have occurred in the afternoon of the session examined.
A study of a numerical simulation by the NASA Ames Mars General
Circulation Model (MGCM) showed prominent minima and maxima, resembling
those observed by MPF, in the diurnal pressure cycles of simulated sols
corresponding to the Presidential sessions. Also well simulated in each sol is the
very rapid increase in surface pressure immediately after the daily minimum.
Maps of diurnal and semidiurnal tidal amplitudes for the simulated Presidential
sols show that tidal harmonic amplitudes are very spatially dependent, and
that large changes in the harmonic amplitudes at any given location are likely
to result if the global amplitude pattern for one or more frequencies undergoes
small shifts in areographic location.
Simulated temperature has a classic "red" power spectrum, while simulated
pressure power is concentrated in the tidal frequency range. These spectral
shapes are roughly consistent with those computed from the MPF Presidential
sessions. The ratios of simulated to observed temperature power spectral estimates
for frequencies from 1 to 50 cycles/sol show that the MGCM's simulated
temperature variability is too low at all frequencies and especially so at higher
frequencies. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28927 |
| Date | 28 April 2003 |
| Creators | Bennett, Scott |
| Contributors | Barnes, Jeffrey R. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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