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On resonant Rossby–Haurwitz triads Cover

On resonant Rossby–Haurwitz triads

By:   
Open Access
|Jan 2009

Abstract

The dynamics of non-divergent flow on a rotating sphere are described by the conservation of absolute vorticity. The analytical study of the non-linear barotropic vorticity equation is greatly facilitated by the expansion of the solution in spherical harmonics and truncation at low order. The normal modes are the well-known Rossby—Haurwitz (RH) waves, which represent the natural oscillations of the system. Triads of RH waves, which satisfy conditions for resonance, are of critical importance for the distribution of energy in the atmosphere.

We show how non-linear interactions of resonant RH triads may result in dynamic instability of large-scale components. We also demonstrate a mathematical equivalence between the equations for an orographically forced triad and a simple mechanical system, the forced-damped swinging spring. This equivalence yields insight concerning the bounded response to a constant forcing in the absence of damping. An examination of triad interactions in atmospheric reanalysis data would be of great interest.

Language: English
Page range: 438 - 445
Submitted on: Aug 21, 2008
Accepted on: Jan 23, 2009
Published on: Jan 1, 2009
Published by: Stockholm University Press
In partnership with: Paradigm Publishing Services

© 2009 Peter Lynch, published by Stockholm University Press
This work is licensed under the Creative Commons Attribution 4.0 License.