Gravity wave variations during the 2009 stratospheric sudden warming as revealed by ECMWF-T799 and observations

The magnitude and occurrence of GWs correlate with the location and strength of the polar vortex that is strongly disturbed by planetary wave (PW) growth. This location dependence on PW phase explains the observed GW variability during SSWs.

During the development and the onset of SSW, the zonal-mean GW potential energy density (GW-Ep) increases on January 5 and 15--22 in association with the growth of PW wavenumber 1 and wavenumber 2, respectively. As the initial prominent PW magnitude in the lower mesosphere progresses downward, GW-Ep enhancement also seems to show a corresponding descent from January 5-22. GW-Ep peaks before the wind reversal occurrence and significantly weakens after the SSW.