Gravity wave variation from the troposphere to the lower thermosphere during a stratospheric sudden warming event: A case study

Monday, April 3, 2017

High resolution Whole Atmosphere Community Climate Model (WACCM) simulations are used to study how gravity waves vary during a stratospheric sudden warming (SSW) event from the source region to the lower thermosphere.

Vertical energy flux image
Vertical energy flux due to pressure work at 30-90km (every 20km, for lower to upper panels) before a major stratospheric sudden warming (SSW) event (left panel) and after the SSW event (right panel), as simulated by high-resolution WACCM. Positive values (red) are for upward energy flux, and negative values (blue) are for downward energy flux.

The variation of zonal mean momentum flux of resolved gravity waves (with zonal wavelengths less than 1600km) during SSW are qualitatively consistent with those obtained from parameterized studies, mainly caused by the change of filtering by the mean zonal wind. Gravity waves are also found to vary as wave sources change. At tropical region (especially in the summer hemisphere), convectively generated gravity waves increase due to enhanced deep convection following SSW. At higher latitudes, orographic waves vary during SSW as the wind changes extend from the stratosphere down into the troposphere. Gravity waves generated from adjustment of the polar jet also undergo significant changes during SSW. These changes lead to strong longitudinal variation of gravity waves.

Publication Name: SOLA : Scientific Online Letters on the Atmosphere