  On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345.
The occultation latitude was 55.5 degrees S. This paper analyzes the 2.3 {\mu}m
light curve derived by Harrington & French. A fixed-baseline isothermal fit to
the light curve has a temperature of 140 +/- 3 K, assuming a mean molecular
mass of 2.35 AMU. The thermal profile obtained by numerical inversion is valid
between 1 and 60 {\mu}bar. The vertical temperature gradient is >0.2 K/km more
stable than the adiabatic lapse rate, but it still shows the
alternating-rounded-spiked features seen in many temperature gradient profiles
from other atmospheric occultations and usually attributed to breaking gravity
(buoyancy) waves. We conduct a wavelet analysis of the thermal profile, and
show that, even with our low level of noise, scintillation due to turbulence in
Earth's atmosphere can produce large temperature swings in light-curve
inversions. Spurious periodic features in the "reliable" region of a wavelet
amplitude spectrum can exceed 0.3 K in our data. We also show that gravity-wave
model fits to noisy isothermal light curves can lead to convincing wave
"detections". We provide new significance tests for localized wavelet
amplitudes, wave model fits, and global power spectra of inverted occultation
light curves by assessing the effects of pre- and post-occultation noise on
these parameters. Based on these tests, we detect several significant ridges
and isolated peaks in wavelet amplitude, to which we fit a gravity wave model.
We also strongly detect the global power spectrum of thermal fluctuations in
Saturn's atmosphere, which resembles the "universal" (modified Desaubies) curve
associated with saturated spectra of propagating gravity waves on Earth and
Jupiter.
