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Simulation of the eastward 4-day wave in the Antarctic winter mesosphere using a gravity wave resolving general circulation model

Authors :
Yoshio Kawatani
Kaoru Sato
Yoshihiro Tomikawa
Masaaki Takahashi
Kazuyuki Miyazaki
Shingo Watanabe
Source :
Journal of Geophysical Research. 114
Publication Year :
2009
Publisher :
American Geophysical Union (AGU), 2009.

Abstract

[1] The eastward moving 4-day wave in the Antarctic winter mesosphere is investigated using a high-resolution middle atmosphere general circulation model that directly simulates the spontaneous generation, propagation, and dissipation of gravity waves. The results are also compared with the simulated seasonal march of the meridional structures of the westerly jet streams in the Southern Hemisphere upper stratosphere and mesosphere in order to investigate baroclinic/barotropic instability as a possible excitation mechanism for the 4-day wave. The model successfully reproduces the dynamically unstable double-jet structure of the mesospheric westerly winds. The simulated 4-day wave develops in association with the baroclinic and barotropic instability of the mesospheric mean flows and has similar characteristics to those observed at 50–60°S near the stratopause. The 4-day wave has strong equatorward heat flux associated with strong baroclinicity in the Antarctic winter mesosphere, mainly attributable to poleward overturning circulation driven by gravity wave forcing. Eastward forcing due to the 4-day wave occurs within the double-jet structure and offsets part of the westward forcing due to gravity waves. Such an effect partially acts to stabilize the unstable mean flow structure in the Antarctic winter mesosphere.

Details

ISSN :
01480227
Volume :
114
Database :
OpenAIRE
Journal :
Journal of Geophysical Research
Accession number :
edsair.doi...........16083bf478a893143b6b5fa0d74bf82e
Full Text :
https://doi.org/10.1029/2008jd011636