Clouds, Hazes, And Methane In The Atmospheres Of Uranus And Neptune: An Analysis Of Spatially Resolved, Near Infrared Spectra
Spatially resolved, near-infrared spectral observations of Uranus and Neptune are presented and analyzed in this study of the ice giant atmospheres. Using radiative transfer analysis and a sophisticated constrained retrieval algorithm, the distribution of aerosols and methane gas were retrieved from H and K-band near-infrared spectra. These observations cover a range of latitudes and times between 2001 and 2007, permitting significant spatial and temporal variance in the retrieved quantities. Two layers of aerosols are needed to match the near-IR observations of both Uranus and Neptune. The upper layer peaks near the tropopause on Uranus and in the lower stratosphere on Neptune. The layer is considerably thicker and more variable on Neptune, producing the prominent clouds visible in near-IR images of Neptune. The lower cloud peaked at ~2.1 and ~2.3 bars for Uranus and Neptune, respectively, with variations in latitude that are interpreted in context of notional circulation models. Temporal changes suggest potential seasonal effects in the case of Uranus and intraseasonal variation on Neptune. Retrievals of the methane mole fraction are consistent with polar depletion on both planets, although Neptune has more methane at the tropopause with which to produce condensate. Finally, high clouds on each planet are considered in terms of parcel theory with the goal of understanding formation mechanisms. The low scattering optical depths of discrete high clouds are consistent with formation associated with vortices and shallow lift rather than deep convection.
Uranus; Neptune; Atmospheres
Veverka,Joseph Frank; Hess,Peter George Mueller; Banfield,Donald J
Ph. D., Atmospheric Science
Doctor of Philosophy
dissertation or thesis