Effects of latitude-dependent gravity wave source variations on the middle and upper atmosphere

TL;DR

This study uses a 3D general circulation model with GW parameterization to analyze how latitude-dependent gravity wave sources influence the middle and upper atmosphere, improving simulation accuracy with observational data.

Contribution

It introduces a model incorporating latitude-dependent GW source variations, enhancing the simulation of atmospheric wave activity and circulation compared to previous approaches.

Findings

Smaller GW fluxes are needed at the source to match observations.

Accounting for latitudinal variations improves simulation accuracy.

Model results align better with SABER and UARS data when source variations are included.

Abstract

Atmospheric gravity waves (GWs) are generated in the lower atmosphere by various weather phenomena. They propagate upward, carry energy and momentum to higher altitudes, and appreciably influence the general circulation upon depositing them in 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 temperature and total absolute momentum flux, 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 broader spectrum of GWs, while parameterizations capture only a portion relevant to the middle and upper atmosphere dynamics. Accounting for the latitudinal variations of the source appreciably improves simulations.