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SUMMARY:Evidence for non-radiative dissipation of stratospheric Kelvin wav
 es - Peter Hitchcock\, Ecole Polytechnique
DTSTART:20180620T100000Z
DTEND:20180620T110000Z
UID:TALK107500@talks.cam.ac.uk
CONTACT:9780
DESCRIPTION:Satellite-born observations of the occultation of radio signal
 s emitted by global navigational system satellites (e.g. GPS) provide high
  quality measurements of temperature profiles in the upper troposphere and
  lower stratosphere. For the past decade or so a constellation of satellit
 es have been providing a large number of such profiles around the globe\, 
 with sufficient spatial and temporal coverage to provide detailed informat
 ion about large-scale waves in this region of the atmosphere.\n\nIn partic
 ular\, the vertical propagation equatorial Kelvin waves can be very well o
 bserved. The behaviour of Kelvin wave packets within the stratosphere is i
 n very close agreement with theoretical expectations from linear theory on
  a weakly varying backround state. However\, estimates of the dissipation 
 of these waves due to radiative processes are not sufficient to explain th
 e observed attenuation of these waves within the vertical shear zones asso
 ciated with the quasi-biennial oscillation\, suggesting that a non-radiati
 ve process is responsible for nearly half of the dissipation of these wave
 s. The plausibility of alternative dissipation mechanisms will also be dis
 cussed.\n\nSince the dissipation of these waves plays a central role in pr
 oducing the quasi-biennial oscillation\, a better understanding of the mec
 hanisms responsible should be of value for efforts to model this phenomeno
 n in global models of the atmospheric circulation.\n
LOCATION:MR12\, Centre for Mathematical Sciences
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