Gravity Wave Source Variations and Their Impacts during the 2009 Stratospheric Sudden Warming
Abstract
Gravity waves (GW) are one of the key elements for driving the atmospheric coupling from the stratosphere to the thermosphere during stratospheric sudden warmings (SSWs). The limited knowledge of GW variations and their source distribution leads to the uncertainty in the SSW simulations by general circulation models. In this study, ECMWF-T799 (0.25° horizontal resolution and 91 vertical levels up to 0.01 hPa) is used to study the causes of GW variations and the impacts of these GW variations on the stratosphere and the lower mesospheric dynamics during the 2009 SSW. ECMWF shows that overall GWs enhance prior to the 2009 SSW. The magnitude and occurrence of GWs correlate with the location and strength of the polar vortex that is strongly distorted by planetary wave (PW) growth. During the development and 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. These variations are confirmed by COSMIC/GPS observations. To better understand the causes of these GW variations, the statistical study of GW source variations along with case study of in-situ GW generation by spontaneous adjustment process will be addressed. The impacts of these enhanced GWs are estimated by comparing PW and GW forcing and residual circulations in the stratosphere and the lower mesosphere, which help us understand the mechanisms of atmospheric coupling associated with SSWs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMSA31B1726Y
- Keywords:
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- 3319 ATMOSPHERIC PROCESSES / General circulation;
- 3334 ATMOSPHERIC PROCESSES / Middle atmosphere dynamics;
- 3384 ATMOSPHERIC PROCESSES / Acoustic-gravity waves;
- 3389 ATMOSPHERIC PROCESSES / Tides and planetary waves