Nonlinear critical layer interactions of wave packets in the atmosphere

A mathematical difficulty that arises in the linear, inviscid theory of waves in shear flows is that a singularity is generally present if there is a point where the mean flow velocity is equal to the phase speed of the perturbation. In the critical layer centred upon such a point, incident waves may be absorbed by the mean flow and, when nonlinear effects are included in the governing equations, wave breaking and reflection sometimes occur. There are several atmospheric phenomena which are known to result from wave-mean-flow interactions, for example, the quasi-biennial oscillation (QBO) which is observed in the tropical stratosphere. In this talk, I shall describe numerical and asymptotic studies of the nonlinear evolution of forced wave packets at critical layers.

Refreshments will be served at 2:45 p.m. in the Faculty Lounge, Math Annex (Room 1115).