Evidence for non-radiative dissipation of stratospheric Kelvin waves

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• Peter Hitchcock, Ecole Polytechnique
• Wednesday 20 June 2018, 11:00-12:00
• MR12, Centre for Mathematical Sciences.

If you have a question about this talk, please contact phh1.

Satellite-born observations of the occultation of radio signals 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 satellites have been providing a large number of such profiles around the globe, with sufficient spatial and temporal coverage to provide detailed information about large-scale waves in this region of the atmosphere.

In particular, the vertical propagation equatorial Kelvin waves can be very well observed. The behaviour of Kelvin wave packets within the stratosphere is in 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 the observed attenuation of these waves within the vertical shear zones associated with the quasi-biennial oscillation, suggesting that a non-radiative process is responsible for nearly half of the dissipation of these waves. The plausibility of alternative dissipation mechanisms will also be discussed.

Since the dissipation of these waves plays a central role in producing the quasi-biennial oscillation, a better understanding of the mechanisms responsible should be of value for efforts to model this phenomenon in global models of the atmospheric circulation.

This talk is part of the DAMTP Atmosphere-Ocean Dynamics series.

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