Other
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p23e..09m&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P23E-09
Other
[0343] Atmospheric Composition And Structure / Planetary Atmospheres, [3334] Atmospheric Processes / Middle Atmosphere Dynamics, [6005] Planetary Sciences: Comets And Small Bodies / Atmospheres
Scientific paper
Polar Warming (PW) is a dynamical feature of the Martian atmosphere that consists of a temperature enhancement over mid-to-high latitudes during winter, spring, and autumn. It produces a reversal of the meridional temperature gradient and temperature inversions over mid-to-high latitudes. This phenomenon is the result of a global Hadley circulation which is a thermally-direct response to diabatic forcing caused by: (a) differential insolation, and (b) absorption of solar infrared radiation by suspended dust [1-4]. Previous studies of PW [5-9] have been limited by data paucity. Consequently, several important aspects of PW climatology have gone unknown. Now, sufficient data is available for in-depth characterization of the structure and variability of this phenomenon in the middle atmosphere [manuscript in preparation]. In this paper we define a warming index and characterize PW as observed by MCS/MRO, SPICAM/Mars Express, and the accelerometer experiments that flew on MGS, Mars Odyssey, and MRO. During most seasons, PW manifests between p = 1-10 Pa and the top of the MCS dataset, and during seasons where SPICAM and ACC data are available, warming often persists through the extent of these data as well (i.e., up to p = 1.0 x 10-4 Pa). PW maximizes in the vertical between p = 1.9 to 0.5 Pa. We find the latitude of maximum temperature tends to move pole-ward with decreasing pressure, indicating a pole-ward slant with height of the descending branch of the Hadley cell. We find PW tends to be stronger on the nightside than on the dayside. As expected from previous studies, we find PW is stronger during northern winter solstice (Ls = 270°) than during southern winter solstice (Ls = 90°). Interestingly, however, we find PW in both the northern hemisphere and the southern hemisphere is stronger during Ls = 180° than during other seasons. This is unexpected because: (a) early studies focused on PW as strictly a winter phenomenon, and (b) dust optical depth is generally smaller during this period than during northern winter. Another interesting discovery is that during both equinoxes, PW is stronger in the southern hemisphere than in the northern hemisphere. While there is not much deviation from these general trends from one MY to the next, the magnitude of PW does exhibit significant inter-annual variability. If time permits, we will discuss initial efforts to reproduce these observed PW patterns and variability with the extended Mars-WRF GCM [10].
Bougher Stephen W.
Forget Francois
Kleinboehl Armin
McDunn T. L.
Mischna Michael A.
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