Thermal Radiative Fluxes in Jupiter's Atmosphere: Implications of the Galileo Probe Net Flux Radiometer Results.
Abstract
The Galileo Probe Net Flux Radiometer (NFR) made in situ observations of the up-welling and net solar and thermal radiative fluxes in the Jovian atmosphere from the 0.4-bar level down to around 13 bars. Thermal flux measurements were made in three spectral channels: a broadband channel (A, 3.5--200 mu m); a longwave channel (D, 14--35 mu m); and a 5-mu m window channel (C, 3.5--5.8 mu m). Preliminary results were presented by Sromovsky et al. (Science, 272, pp. 851--854, 1996). A two-stream line-by-line radiative transfer model was used to calculate the observed net and up-fluxes in the thermal channels. The net fluxes measured in both channels A and C were much larger than would be expected for near-solar abundances of water vapour and ammonia. It is found that a reduction in the volume mixing ratio of H_2O to 10% of the solar value in the deep atmosphere (below the 6-bar level) is required to match the observations. There is no indication of the predicted massive water cloud near 5 bars but there is evidence for clouds at 1.35 bars and 0.6 bars which would correspond to the predicted NH_4SH and NH_3 layers respectively. High channel A net fluxes in the early part of the descent imply very low abundances of NH_3 at pressures below 1 bar. The derived cloud properties and abundances of NH_3 and H_2O are used to simulate total thermal flux profiles and heating rates, and the observations that would be expected from the Voyager IRIS experiment and ground-based observations from the NASA IRTF CSHELL instrument. This research was supported by the Galileo project through a grant from the NASA Ames Research Center.
- Publication:
-
AAS/Division for Planetary Sciences Meeting Abstracts #28
- Pub Date:
- September 1996
- Bibcode:
- 1996DPS....28.2104C