DPS 2001 meeting, November 2001
Session 7. Outer Planet Atmospheres I: Dynamics and Clouds
Oral, Chairs: A. Showman, P. Yanamandra-Fisher, Tuesday, November 27, 2001, 3:50-5:00pm, Regency E

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[7.01] Fresh Ammonia Ice Clouds in Jupiter: Recent Views by Galileo/NIMS, and Implications for Rossby Waves and Vertical Transport

K. H. Baines, R. W. Carlson, L. W. Kamp, A. J. Friedson (JPL/Caltech)

While most of the optically-thick clouds observed on Jupiter are expected to be composed primarily of ammonia condensates, a global survey conducted by Galileo/NIMS in September, 1996 has revealed that spectrally-identifiable ammonia clouds (SIAC's) cover just ~ 0.5% of the area of the planet. Such clouds, identified principally by the anomalous absorption observed near the 2.73 micron atmospheric continuum, seem to be correlated with regions associated with strong dynamical phenomena near the ammonia condensation level, indicating that they are freshly-formed cloud features. The majority of such clouds (55%) are found within the northern equatorial belt, centered 1.5 degrees south and about 15 degrees east of nearby hotspots. The good spatial correlation between the most spectrally-strong ammonia clouds and nearby hotspots suggests a common origin, such as a three-dimensional planetary Rossby wave. To test the wave hypothesis, a region of hotspots and SIACs were repeatedly mapped by NIMS over a 31-hour period during the recent C30 orbit (May 24-25,2001) and examined for relative movement between the features. A common wave origin would imply that the hotspots and SIACS would remain relatively stationary to each other. On the other hand, advection by the local windfield, as determined by the Galileo probe, would imply that the SIACs located at about the 400 mbar level would move about 4.5 degrees of longitude relative to the hotspots located at about 2.0 bar. Initial examination of the maps indicates the movement was significantly less than predicted by pure advection, thus supporting a wave hypothesis. Results from enhanced geometric and photometric calibration will be presented.

Detailed mapping of the turbulent wake region northwest of the Great Red Spot was acquired on August 6, 2001, during orbit C31. Our previous global observations in September 1996 showed that the largest and spectrally-strongest SIACs inhabit this region, with a single SIAC to the northwest of the GRS dominating the turbulent wake, with relatively few SIACs apparent to the immediate west and WNW of the GRS. In contrast, the initial data reduction of our most recent observation seems to indicate a different character, with many smaller yet spectrally-strong SIAC's dominating the scene to the west and WNW of the GRS. We will present results from a detailed geometric and photometric calibration of this region upon final receipt of downlinked data, scheduled for October 15, 2001.

The author(s) of this abstract have provided an email address for comments about the abstract: kbaines@aloha.jpl.nasa.gov

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