A Comparison of Stratospheric Gravity Waves in a High-Resolution General
Circulation Model with 3-D Satellite Observations
Abstract
Atmospheric gravity waves (GWs) play a key role in determining the
thermodynamical structure of the Earth’s middle atmosphere. Despite the
small spatial and temporal scales of these waves, a few high-top general
circulation models (GCMs) that can resolve them explicitly have recently
become available. This study compares global GW characteristics
simulated in one such GCM, the Japanese Atmospheric GCM for
Upper-Atmosphere Research (JAGUAR), with those derived from
three-dimensional (3-D) temperatures observed by the Atmospheric
Infrared Sounder (AIRS) aboard NASA’s Aqua satellite. The target period
is from 15 December 2018 to 8 January 2019, including the onset of a
major sudden stratospheric warming (SSW). The 3-D Stockwell transform
method is used for GW spectral analysis. The amplitudes and momentum
fluxes of GWs in JAGUAR are generally in good quantitative agreement
with those in the AIRS observations in both magnitude and distribution.
As the SSW event progressed, the GW amplitudes and eastward momentum
flux increased at low latitudes in the summer hemisphere in both the
model and observation datasets. Case studies demonstrate that the model
is able to reproduce comparable wave events to those in the AIRS
observations with some differences, especially noticeable at low
latitudes in the summer hemisphere. Through a comparison between the
model results with and without the AIRS observational filter applied, it
is suggested that the amplitudes of GWs near the exits and entrances of
eastward jet streaks are underestimated in AIRS observations.