Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003)

Details Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003) Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003)

Jul 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005icar..176..155p&link_type=abstract

Icarus, Volume 176, Issue 1, p. 155-174.

Computer Science

35

Scientific paper

We present a study of the vertical structure of clouds and hazes in the upper atmosphere of Saturn's Southern Hemisphere during 1994 2003, about one third of a Saturn year, based on Hubble Space Telescope images. The photometrically calibrated WFPC2 images cover the spectral region between the near-UV (218 255 nm) and the near-IR (953 1042 nm), including the 890 nm methane band. Using a radiative transfer code, we have reproduced the observed center-to-limb variations in absolute reflectivity at selected latitudes which allowed us to characterize the vertical structure of the entire hemisphere during this period. A model atmosphere with two haze layers has been used to study the variation of hazes with latitude and to characterize their temporal changes. Both hazes are located above a thick cloud, putatively composed of ammonia ice. An upper thin haze in the stratosphere (between 1 and 10 mbar) is found to be persistent and formed by small particles (radii ˜0.2 μm). The lower thicker haze close to the tropopause level shows a strong latitudinal dependence in its optical thickness (typically τ˜20 40 at the equator but τ˜5 at the pole, at 814 nm). This tropospheric haze is blue-absorbent and extends from 50 to 100 mbar to about ˜400 mbar. Both hazes show temporal variability, but at different time-scales. First, there is a tendency for the optical thickness of the stratospheric haze to increase at all latitudes as insolation increases. Second, the tropospheric haze shows mid-term changes (over time scales from months to 1 2 years) in its optical thickness (typically by a factor of 2). Such changes always occur within a rather narrow latitude band (width ˜5 10°), affecting almost all latitudes but at different times. Third, we detected a long-term (˜10 year) decrease in the blue single-scattering albedo of the tropospheric haze particles, most intense in the equatorial and polar areas. Long-term changes follow seasonal insolation variations smoothly without any apparent delay, suggesting photochemical processes that affect the particles optical properties as well as their size. In contrast, mid-term changes are sudden and show various time-scales, pointing to a dynamical origin.

Affiliated with

Also associated with

No associations

Rating

Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003) does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003), we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Saturn's cloud structure and temporal evolution from ten years of Hubble Space Telescope images (1994 2003) will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1251669