Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.5803m&link_type=abstract
American Astronomical Society, DPS meeting #39, #58.03; Bulletin of the American Astronomical Society, Vol. 39, p.533
Astronomy and Astrophysics
Astronomy
Scientific paper
Near Infrared observations of the nightside of Venus reveal regions of high brightness temperatures. These regions of high brightness temperatures are caused by the localized evaporation of the middle and lower cloud decks, which are about 50 to 60 km above the surface of the planet. We simulate the Venus condensational middle and lower cloud deck with the University of Colorado / NASA Ames Community Aerosol and Radiation Model for Atmospheres (CARMA). The lifetimes of these holes are observed to be moderately short, on the order of ten days. We have developed a two-dimensional (zonal, vertical) model with simplified dynamics to study the effects of zonal flow on the lifetimes of the holes in the clouds. We find that although wind shear may be negligible within the middle cloud itself, the shear that is present near the top and the bottom of the statically unstable middle cloud region can lead to changes in the radiative-dynamical feedback which ultimately lead to the dissipation of the holes.
There is observational evidence that indicates the presence of convective motions and gravity waves within the Venus clouds. We also present results of a simple two-dimensional model investigating the observable effects that convective motions and gravity waves can have on the condensational Venus cloud. We find that a simplified treatment of convective dynamics generates variation in the Venus condensational cloud consistent with observed variability. We also find that gravity waves launched by obstacles (such as overshooting convective plumes) near cloud base are capable of generating variations in 1.74-micron brightness temperature that should be observable by instruments such as VIRTIS on Venus Express. However, a more robust treatment of the atmospheric dynamics is needed to address adequately these interactions with the mesoscale dynamics.
This work was supported by NASA's Planetary Atmospheres Program under grant NNG05GA53G.
McGouldrick Kevin
Toon Brian O.
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