Revisiting internal gravity waves analysis using GPS RO density profiles: comparison with temperature profiles and application for wave field stability study
Abstract. We revise selected findings regarding the utilization of Global
Positioning System radio occultation (GPS RO) density profiles for
the analysis of internal gravity waves (IGW), introduced by
 Sacha et al. ( 2014 ) . Using various GPS RO datasets, we show that the
differences in the IGW spectra between the dry-temperature and
dry-density profiles that were described in the previous study as
a general issue are in fact present in one specific data version
only. The differences between perturbations in the temperature and
density GPS RO profiles do not have any physical origin, and there is
not the information loss of IGW activity that was suggested in
 Sacha et al. ( 2014 ) . We investigate the previously discussed question
of the temperature perturbations character when utilizing GPS RO
dry-temperature profiles, derived by integration of the hydrostatic
balance. Using radiosonde profiles as a proxy for GPS RO, we provide
strong evidence that the differences in IGW perturbations between
the real and retrieved temperature profiles (which are based on the
assumption of hydrostatic balance) include a significant
nonhydrostatic component that is present sporadically and might be
either positive or negative. The detected differences in related
spectra of IGW temperature perturbations are found to be mostly
about ±10 % . The paper also presents a detailed study on the utilization of GPS
RO density profiles for the characterization of the wave field
stability. We have analyzed selected stability parameters derived
from the density profiles together with a study of the vertical
rotation of the wind direction. Regarding the Northern Hemisphere
the results point to the western border of the Aleutian high, where
potential IGW breaking is detected. These findings are also
supported by an analysis of temperature and wind velocity
profiles. Our results confirm advantages of the utilization of the
density profiles for IGW analysis.