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SUMMARY:Spontaneous wave generation in geophysical fluids - Jacques Vannes
 te (University of Edinburgh)
DTSTART:20101015T150000Z
DTEND:20101015T160000Z
UID:TALK27004@talks.cam.ac.uk
CONTACT:Dr C. P.  Caulfield
DESCRIPTION:A long-standing issue in geophysical fluid dynamics has been t
 o quantify the coupling between the slow balanced motion\, which dominates
  the large-scale dynamics\, and the much faster inertia-gravity waves. Pio
 neering work by Lorenz in the mid-1980s introduced the idea of near-invari
 ant slow manifolds to characterise the balanced part of the motion. More r
 ecent work has concentrated on mechanisms of spontaneous generation\, wher
 eby inertia-gravity waves are emitted by slowly evolving balanced flows. S
 uch mechanisms demonstrate the fundamental limitations of the concept of s
 low manifold\; they may also constitute significant sources of wave activi
 ty in the atmosphere and ocean.\nIn this talk\, I will consider spontaneou
 s wave generation in the small-Rossby-number (rotation-dominated) regime. 
 In this regime\, there is a strict time-scale separation between balanced 
 motion and inertia-gravity waves. As a result\, slow manifolds can be cons
 tructed that are invariant to all orders on the Rossby number. This implie
 s that wave generation is exponentially weak in the Rossby number and cann
 ot be captured by standard power-series expansions. Exponential asymptotic
 s techniques can however be used to describe the waves generated. I will d
 iscuss the application of these techniques to low-order models and to some
  idealised flows.
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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