Understanding the Cloud Structure on the Giant Planets.

[摘要] The Equilibrium Cloud Condensation Model, or ECCM, is a thermochemical equilibrium model used to predict a multi-layer cloud structure on the giant planets. The model calculates upper limits for the cloud concentrations. In this dissertation, the effect of precipitation on the concentration of Jupiter’s water clouds is explored following the preliminary formulations of cloud microphysics. Precipitation time scales and maximum precipitation rate are calculated to estimate the water cloud concentration more realistically. In another part of the dissertation, the ECCM is combined with microwave radiometry data to assess the composition and structure of clouds in the troposphere of Uranus. In particular, constraints on phosphine are obtained. Phosphine is expected to be in thermochemical equilibrium in the deep troposphere of Uranus. Its presence in the upper troposphere is indicative of deep atmospheric convection. However, no measurements have yet revealed phosphine in the troposphere of the ice giant planets, Uranus and Neptune. Radiative transfer analysis of microwave observations with the Very Large Array radio telescope and the Sub-Millimeter Array were carried out using new phosphine vapor absorption coefficients to determine if phosphine or another species can explain the microwave opacity in the 2 to 6 bar region. Phosphine is found to play a significant role. In the region of the clouds, elemental abundances of phosphorus, nitrogen, oxygen, and sulfur were found to range from 4-10, 0.008-0.6, 0-10, and 0.5-4 times their solar elemental abundances, respectively. It is important to point out that these are only cloud region values, and do not necessarily represent the elemental abundances in the interior of the planet. Nevertheless, the relatively low elemental abundances of nitrogen and oxygen in the upper troposphere of Uranus indicate possible removal of ammonia and water in the interior, perhaps through the formation of an ionic ocean.

[发布机构] University of Michigan

[效力级别] Phosphine

[关键词] Uranus;Phosphine;Jupiter;Microphysics;Clouds;Atmosphere;Atmospheric;Oceanic and Space Sciences;Science;Atmospheric and Space Science