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Post Info TOPIC: Jovian atmosphere
Blobrana


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RE: Jovian atmosphere
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Title: Jupiter's Deep Cloud Structure Revealed Using Keck Observations of Spectrally Resolved Line Shapes
Author: G. L. Bjoraker, M. H. Wong, I. de Pater, M. Adámkovics

Technique: We present a method to determine the pressure at which significant cloud opacity is present between 2 and 6 bars on Jupiter. We use: a) the strength of a Fraunhofer absorption line in a zone to determine the ratio of reflected sunlight to thermal emission, and b) pressure-broadened line profiles of deuterated methane (CH3D) at 4.66 microns to determine the location of clouds. We use radiative transfer models to constrain the altitude region of both the solar and thermal components of Jupiter's 5-micron spectrum. Results: For nearly all latitudes on Jupiter the thermal component is large enough to constrain the deep cloud structure even when upper clouds are present. We find that Hot Spots, belts, and high latitudes have broader line profiles than do zones. Radiative transfer models show that Hot Spots in the North and South Equatorial Belts (NEB, SEB) typically do not have opaque clouds at pressures greater than 2 bars. The South Tropical Zone (STZ) at 32 degrees S has an opaque cloud top between 4 and 5 bars. From thermochemical models this must be a water cloud. We measured the variation of the equivalent width of CH3D with latitude for comparison with Jupiter's belt-zone structure. We also constrained the vertical profile of water in an SEB Hot Spot and in the STZ. The Hot Spot is very dry for P<4.5 bars and then follows the water profile observed by the Galileo Probe. The STZ has a saturated water profile above its cloud top between 4 and 5 bars.

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Blobrana


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Kelvin wave
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NASA Scientists Identify Missing Wave near Jupiter's Equator

In the clouds of Jupiter, scientists have found evidence of a type of atmospheric wave that had long been proposed but had not been identified in images before now.
Researchers consider this kind of wave, called a Kelvin wave, a fundamental part of a planetary atmosphere, so the absence of one on Jupiter has long been a mystery. In Earth's atmosphere, Kelvin waves are involved in a tropical wind pattern whose influence can reach as far as the polar vortex.
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Blobrana


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Posts: 131433
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Jovian atmosphere
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Title: The source of widespread 3-µm absorption in Jupiter's clouds: Constraints from 2000 Cassini VIMS observations
Author: Lawrence Sromovsky, Patrick Fry

The Cassini flyby of Jupiter in 2000 provided spatially resolved spectra of Jupiter's atmosphere using the Visual and Infrared Mapping Spectrometer (VIMS). These spectra contain a strong absorption at wavelengths from about 2.9 µm to 3.1 µm, previously noticed in a 3-µm spectrum obtained by the Infrared Space Observatory (ISO) in 1996. While Brooke et al. (1998, Icarus 136, 1-13) were able to fit the ISO spectrum very well using ammonia ice as the sole source of particulate absorption, Sromovsky and Fry (2010, Icarus 210, 211-229), using significantly revised NH3 gas absorption models, showed that ammonium hydrosulfide (NH4SH) provided a better fit to the ISO spectrum than NH3 , but that the best fit was obtained when both NH3 and NH4SH were present. Although the large FOV of the ISO instrument precluded identification of the spatial distribution of these two components, the VIMS spectra at low and intermediate phase angles show that 3-µm absorption is present in zones and belts, in every region investigated, and both low- and high-opacity samples are best fit with a combination of NH4SH and NH3 particles at all locations. The best fits are obtained with a layer of small ammonia-coated particles (r~0.3 µm) overlying but often close to an optically thicker but still modest layer of much larger NH4SH particles (r~10 µm), with a deeper optically thicker layer, which might also be composed of NH4SH. Although these fits put NH3 ice at pressures less than 500 mb, this is not inconsistent with the lack of prominent NH3 features in Jupiter's longwave spectrum because the reflectivity of the core particles strongly suppresses the NH3 absorption features, at both near-IR and thermal wavelengths.

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Blobrana


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Jupiter's atmosphere
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'Hot Spots' Ride a Merry-Go-Round on Jupiter

In the swirling canopy of Jupiter's atmosphere, cloudless patches are so exceptional that the big ones get the special name "hot spots." Exactly how these clearings form and why they're only found near the planet's equator have long been mysteries. Now, using images from NASA's Cassini spacecraft, scientists have found new evidence that hot spots in Jupiter's atmosphere are created by a Rossby wave, a pattern also seen in Earth's atmosphere and oceans. The team found the wave responsible for the hot spots glides up and down through layers of the atmosphere like a carousel horse on a merry-go-round.
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Blobrana


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RE: Jovian atmosphere
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Title: Power Spectral Analysis of Jupiter's Clouds and Kinetic Energy from Cassini
Authors: David S. Choi, Adam P. Showman

We present suggestive evidence for an inverse energy cascade within Jupiter's atmosphere through a calculation of the power spectrum of its kinetic energy and its cloud patterns. Using Cassini observations, we composed full-longitudinal mosaics of Jupiter's atmosphere at several wavelengths. We also utilised image pairs derived from these observations to generate full-longitudinal maps of wind vectors and atmospheric kinetic energy within Jupiter's troposphere. We computed power spectra of the image mosaics and kinetic energy maps using spherical harmonic analysis. Power spectra of Jupiter's cloud patterns imaged at certain wavelengths resemble theoretical spectra of two-dimensional turbulence, with power-law slopes near -5/3 and -3 at low and high wavenumbers, respectively. The slopes of the kinetic energy power spectrum are also near -5/3 at low wavenumbers. At high wavenumbers, however, the spectral slopes are relatively flatter than the theoretical prediction of -3. Our results also show the importance of calculating spectral slopes from full 2D velocity maps rather than 1D zonal mean velocity profiles, since at large wavenumbers the spectra differ significantly, though at low wavenumbers, the 1D zonal and full 2D kinetic energy spectra are practically indistinguishable. Furthermore, the difference between the image and kinetic energy spectra suggests some caution in the interpretation of power spectrum results solely from image mosaics and its significance for the underlying dynamics. Finally, we also report prominent variations in kinetic energy within the equatorial jet stream that appear to be associated with the 5 µm hotspots. Other eddies are present within the flow collar of the Great Red Spot, suggesting caution when interpreting snapshots of the flow inside these features as representative of a time-averaged state.

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Blobrana


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Jupiter: Turmoil from Below, Battering from Above

Jupiter, the mythical god of sky and thunder, would certainly be pleased at all the changes afoot at his namesake planet. As the planet gets peppered continually with small space rocks, wide belts of the atmosphere are changing colour, hotspots are vanishing and reappearing, and clouds are gathering over one part of Jupiter, while dissipating over another. The results were presented today by Glenn Orton, a senior research scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., at the American Astronomical Society's Division for Planetary Sciences Meeting in Reno, Nev.
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Blobrana


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Title: Nebular water depletion as the cause of Jupiter's low oxygen abundance
Authors: Olivier Mousis, Jonathan I. Lunine, Nikku Madhusudhan, Torrence V. Johnson

Motivated by recent spectroscopic observations suggesting that atmospheres of some extrasolar giant-planets are carbon-rich, i.e. carbon/oxygen ratio (C/O) \ge 1, we find that the whole set of compositional data for Jupiter is consistent with the hypothesis that it be a carbon-rich giant planet. We show that the formation of Jupiter in the cold outer part of an oxygen-depleted disk (C/O ~1) reproduces the measured Jovian elemental abundances at least as well as the hitherto canonical model of Jupiter formed in a disk of solar composition (C/O = 0.54). The resulting O abundance in Jupiter's envelope is then moderately enriched by a factor of ~2 x solar (instead of ~7 x solar) and is found to be consistent with values predicted by thermochemical models of the atmosphere. That Jupiter formed in a disk with C/O ~1 implies that water ice was heterogeneously distributed over several AU beyond the snow line in the primordial nebula and that the fraction of water contained in icy planetesimals was a strong function of their formation location and time. The Jovian oxygen abundance to be measured by NASA's Juno mission en route to Jupiter will provide a direct and strict test of our predictions.

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