Effects of latitude-dependent gravity wave source variations on the
middle and upper atmosphere
Abstract
Atmospheric gravity waves (GWs) are generated globally in the lower
atmosphere by various weather phenomena during all seasons. They
propagate upward, carry a significant amount of energy and momentum to
higher altitudes, and significantly influence the general circulation of
the middle and upper atmosphere. We use a three-dimensional
first-principle general circulation model (GCM) with an implemented
nonlinear whole atmosphere GW parameterization to study the global
climatology of wave activity and produced effects at altitudes up to the
upper thermosphere. The numerical experiments were guided by the GW
momentum fluxes and temperature variances as measured in 2010 by the
SABER (Sounding of the Atmosphere using Broadband Emission Radiometry)
instrument onboard NASA’s TIMED (Thermosphere Ionosphere Mesosphere
Energetics Dynamics) satellite. This includes the latitudinal dependence
and magnitude of GW activity in the lower stratosphere for the boreal
summer season. The modeling results were compared to the SABER and Upper
Atmosphere Research Satellite (UARS) data in the mesosphere and lower
thermosphere. Simulations suggest that, in order to reproduce the
observed circulation and wave activity in the middle atmosphere, smaller
than the measured GW fluxes have to be used at the source level in the
lower atmosphere. This is because observations contain a broad spectrum
of GWs, while parameterizations capture only a portion relevant to the
middle and upper atmosphere. Accounting for the latitudinal variations
of the source appreciably improves simulations.