A seasonal model of the Saturnian upper troposphere: Comparison with Voyager infrared measurements |
| |
| Authors: | Bruno Bézard Daniel Gautier Barney Conrath |
| |
| Institution: | Laboratoire d''Astronomie Infrarouge, Observatoire de Meudon, 92195 Meudon Principal Cédex, France;Laboratory for Extraterrestrial Physics, Goddard Space Flight Center, Greenbelt, Maryland 20771, USA |
| |
| Abstract: | An extension of the seasonal climate model of R. D. Cess and J. Caldwell (1979, Icarus, 38, 349–357) to Saturn's upper troposphere is presented. The ring-modulated latitudinal dependence of the insolation, the ring thermal emission, the oblateness of the planet, the orbit eccentricity, and the latitudinal variation of the internal heat flux are taken into account. Calculations agree closely with the temperature—latitude profiles retrieved from Voyager IRIS measurements at atmospheric levels located above the 0.2-bar pressure level; they reproduce the observed large-scale hemispheric asymmetry which is then shown to result from the seasonally variable insolation. Aerosol absorption is found to be the dominant source of atmospheric solar heating in the troposphere and the model suggests an aerosol mean unit optical depth around the 0.25-bar level in the equatorial region and around the 0.35-bar level at other latitudes. The model fails to predict the retrieved temperature—latitude profiles below the 0.3-bar level. This discrepancy is attributed to the existence of clouds at these levels which are responsible for an additional far-infrared opacity not taken into account in the temperature retrieval. The cloud-top altitude would be about 0.3 bar except in the 20 to 40°N region where these clouds would be confined below the 0.6-bar level. The poor correlation between infrared measurements and visible images is discussed and a possible model of Saturn's cloud structure is proposed. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
