Long-short wave interactions in the atmospheric dynamics

Abstract

The stratified atmosphere supports a variety of wave motion which play a crucial role in weather and climate. The waves can be generated by mountains, storms, and inherent instabilities in the atmospheric flows. They transport and redeposit energy in the flow, often mixing the fluid and thus contributing to setting the very stratification profile which supports the waves. The topic of this proposal is the study of the nonlinear interaction of these wave modes. This means that very different wave modes can exchange energy and therefore lead to considerable change in the observed velocity and pressure fields. The strongest form of interaction is resonant interaction whereby, if some conditions are satisfied in a set of waves, they will exchange substantial energy. Large scale equatorial and mid-Iatitude waves differ considerably from each other and both will be considered. The change of sign of the Coriolis term between north and south localises travelling wave modes near the Equator. This equatorial waveguide, and the background set by the Hadley cells, create a strong barrier between the Northern and Southern Hemispheres and it is thought that "teleconnections"through wave interaction are one of the few methods to cross that barrier. (AU)