Microphysical modeling of clouds in Titan's atmosphere

Details Microphysical modeling of clouds in Titan's atmosphere Microphysical modeling of clouds in Titan's atmosphere

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004phdt.........9b&link_type=abstract

Thesis (PhD). UNIVERSITY OF COLORADO AT BOULDER, Source DAI-B 65/06, p. 2967, Dec 2004, 137 pages.

Physics

Scientific paper

Theoretical arguments point to and recent observations confirm the existence of clouds in Titan's atmosphere, yet we possess very little data on their size, composition, location and formation mechanism. A time- dependent microphysical model is used to study the evolution of ice clouds in Titan's atmosphere. The model simulates nucleation, condensational growth, evaporation, coagulation, and transport of particles in a column of atmosphere. Voyager temperature and density profiles are used to create Titan conditions. Additional data is provided through lab measurements, particularly the nucleation parameters for ethane, methane, and tholin combinations (where tholin refers a laboratory-created analog for Titan's haze particles). A variety of cloud compositions are studied, including pure ethane clouds, pure methane clouds, and mixed methane- ethane clouds (all with tholin cores). Model results are run through a radiative transfer model to determine the impact of the clouds on Titan's albedo. The abundance of methane cloud particles is limited by the number of ethane nuclei rather than the number of tholins. The condensation of methane onto these mixed cloud particles is sufficient to keep the methane close to saturation. Typical methane supersaturations are of order 0.06 on the average, however dynamically induced temperature changes can produce time varying supersaturations. Cloud production does not require a continuous surface source of methane. However, clouds produced by mean motions are not the visible methane clouds seen in recent HST and ground-based observations. Ethane clouds in the troposphere almost instantaneously nucleate methane to form mixed clouds. However, a thin ethane ‘haze’ remains just above the tropopause for some scenarios and the mixed clouds at the tropopause remain ≤50% ethane by mass. Also, evaporation of methane on the mixed cloud particles near the surface leaves a thicker layer of ethane cloud particles at ˜10 km. Short-lived optically thick clouds can be created sporadically by dynamically driven atmospheric cooling. Horizontal quasi-barotropic motions are more likely to drive the supersaturation creating these clouds than are vertical motions. We expect to find these optically thick, mostly methane clouds at the pole where they can be observed by the VIMS, ISS and CIRS instruments on the Cassini orbiter. Additional instruments on the Cassini orbiter, such as UVIS and the Cassini Radar, will provide useful constraints on the input parameters in our microphysics model.

Affiliated with

Also associated with

No associations

Rating

Microphysical modeling of clouds in Titan's atmosphere does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Microphysical modeling of clouds in Titan's atmosphere, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Microphysical modeling of clouds in Titan's atmosphere will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1164089