[GTP] GTP Seminar May 6, 2013

[Carolyn Mueller]

Just a reminder of Monday's seminar.


On 4/30/2013 9:00 AM, Carolyn Mueller wrote:
> GTP Seminar
>
> AN OCEANIC ULTRA-VIOLET CATASTROPHE, WAVE-PARTICLE DUALITY AND A 
> STRONGLY NONLINEAR CONCEPT OF GEOPHYSICAL TURBULENCE
> Kurt Polzin
>  Woods Hole Oceanographic Institution
>
> Monday, May 6, 2013
> Mesa Lab Main Seminar Room
> Lecture at 3:30pm
>
> Nonlinear interactions between high frequency internal waves 
> interacting with larger vertical and horizontal scale waves having 
> inertial frequency are investigated using ray tracing techniques, 
> analytic approximations to kinetic equations, solutions for the 
> moments of a diffusive approximation to the resonant kinetic equation 
> and Taylor's identity for relative dispersion.  Tracing high frequency 
> waves in one and two inertial wave backgrounds demonstrates that the 
> infinitesimal amplitude and finite amplitude limits are 
> phenomenologically distinct: the finite amplitude state is 
> characterized by the coalescing of the two small scale members of the 
> triad and a transition to a bound wave phenomena.  This coalescence 
> marks the transition from the coupled oscillator paradigm to a 
> particle (wave packet) in a potential well paradigm. Tracing high 
> frequency waves in stochastic inertial wave backgrounds does not 
> reveal any such transition.  Rather, the ray tracing results are 
> phenomenologically consistent with the particle in a (stochastic) well 
> paradigm, independent of amplitude.
>
> Tracing high frequency waves in a stochastic background of inertial 
> oscillations also provides estimates of the temporal evolution for the 
> ensemble mean and variance of vertical wavenumber of a test wave 
> distribution.  These estimates are compared to the evolution of the 
> first and second moments of a diffusive approximation to the resonant 
> kinetic equation.  The diffusive closure manages to describe the 
> evolution of the first two moments at energy levels an order of 
> magnitude smaller than background oceanic values and predicts {\em no} 
> transport of action to smaller scales.  At realistic energy levels the 
> growth of the second moment is inhibited relative to the first, 
> implying a finite downscale action transport.  We demonstrate using 
> Taylor's identity for relative dispersion that the transition occurs 
> when the interaction timescale becomes smaller than the decorrelation 
> time scale of the interaction process.  We argue that the action 
> transport in this parameter regime is the averaged product of particle 
> size (action density) and velocity (time rate of change of the first 
> moment).  This concept is the genesis for the heuristically motivated 
> Finescale Parameterization which summarizes current knowledge relating 
> turbulent dissipation to finescale internal wave spectra.
>
>
>

-- 
Carolyn Mueller
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 80305
http://www2.image.ucar.edu/
Tel: 303 497-2491
Fax: 303-497-2483