  We present a radiative transfer analysis of latitudinally resolved H
(1.487-1.783 micron) and K (2.028-2.364 micron) band spectra of Uranus, from
which we infer the distributions of aerosols and methane in the planet's
atmosphere. Data were acquired in 2001, 2002, 2004, 2005, and 2007 using the
200-inch (5.1 m) Hale Telescope and the Palomar High Angular Resolution
Observer (PHARO) near-infrared adaptive optics (AO) camera system (Hayward,
2001). Observations sample a range of latitudes between 80-deg S and 60-deg N
on the Uranian disk. At each latitude, a vertical distributions of aerosols was
retrieved using a custom non-linear constrained retrieval algorithm. Two layers
of aerosols are needed to match the observations: a thin upper layer peaking
just below the 100-mb tropopause and a lower clouds at ~1.9 bars. Latitudinal
variations in aerosols are interpreted in context of notional circulation
models, while temporal changes suggest potential seasonal effects. We infer
significant reduction in aerosol scattering optical thickness in southern
latitudes between 2001 and 2007, in agreement with trends reported in studies
covering part of the same period using different data and retrieval algorithms
(e.g., Irwin et al., 2009, 2010, 2012; Sromovsky et al., 2009). Best fits to
the data are consistent with proposed models of polar depletion of methane
(e.g., Karkoschka and Tomasko, 2011). Finally, a discrete cloud from 2007 is
analyzed in context of simple parcel theory, with the goal of identifying
likely formation mechanisms. The low scattering optical thicknesses of the
discrete high cloud are consistent with formation associated with vortices and
shallow lift rather than deep convection.
