HR: 0830h
AN: P51C-0465 [PDF]
TI: Characteristics of Saturn's Atmosphere from Ground-Based Thermal Infrared Remote Sensing
AU: * Orton, G S
EM: go@orton.jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Fisher, B
EM: Brendan.Fisher@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Yanamandra-Fisher, P
EM: padma@durga.jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Baines, K
EM: kbaines@aloha.jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Ressler, M
EM: ressler@cheetah.jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Beach-Kimball, B
AF: Wesleyan University, Wesleyan Station, Middletown, CT 06459 United States
AU: Jackson, B
AF: Georgia Institute of Technology, 219 Uncle Heine Way, Atlanta, GA 30032 United States
AU: Gezari, D
AF: NASA Goddard Space Flight Center, Code 685, Greenbelt, MD 20771 United States
AU: Varosi, F
AF: Univeristy of Florida, Department of Astronomy, Gainesville, FL 32611 United States
AB:
Several years of observations of Saturn, obtained primarily at NASA's Infrared Telescope Facility, establish a baseline
against which data from the Cassini Composite Infrared Spectrometer (CIRS) and other remote-sensing instruments can be
compared. Thermal emission at 5.2 $\mu$m, sensitive to clouds near and above the 2--3 bar level, finds them to be strikingly
inhomogeneous with large zonal variations near
the equator and 45$^\circ$S. At longer wavelengths, stratospheric temperatures near 10 mbar are sensed by 7.85-$\mu$m CH$_4$
emission and (with C$_2$H$_6$ abundance variations sensed by 12.2 $\mu$m C$_2$H$_6$ emission). Trosospheric temperatures
near 100--400 mbar are sensed by H$_2$ collision-induced emission between 17 and 24 $\mu$m.
Strong seasonal forcing of stratospheric temperatures is evident, with temperatures tracking the insolation variations with
little time delay, inconsistent with purely radiative equilibrium condistions. Stratospheric temperature (or C$_2$H$_6$
abundance) peaked sharply poleward of 81$^\circ$S latitude in a high-resolution Keck image in 1998. Meridional variations of
stratospheric and tropospheric temperature are not strongly correlated with one another. Planetary-scale zonal waves as
large as 1 Kelvin amplitude are seen in the stratospheric temperature field, with some evidence for even larger-amplitude
waves in the troposphere. Similar to vortices in Titan and Jupiter, we might expect Cassini to detect a polar vortex ({\it
e.g.} a region of depressed temperatures with a sinusoidal boundary), if driven by the seasonal loss of insolation poleward
of its arctic circle.
This work was supported by funds from NASA to the Jet Propulsion Laboratory, California Institute of Technology and the
Goddard Space Flight Center. Brett Beach-Kimball was supported by the Undergraduate Student Researcher Program
(USRP); Brian Jackson was supported by JPL as a Caltech Summer Undergraduate Research Fellow.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 5700 PLANETOLOGY: FLUID PLANETS
DE: 5704 Atmospheres--composition and chemistry
DE: 5757 Remote sensing
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting