Location
MC 5501
Speaker
Alain Gervais, University of Waterloo
Title
Transmission of Atmospheric Internal Gravity Wave Packets across Retrograde Jets
Abstract
Internal gravity waves (IGWs) propagate horizontally and vertically within stably stratified fluids, in which the background mass density decreases with height. IGWs typically exist as packets – spatially localized groups of waves that travel together. If their amplitude is sufficiently large, IGW packets induce an order amplitude-squared mean flow that accelerates the fluid in the vicinity of the waves, leading to amplitude growth which can result in wave overturning, turbulent wave breaking, and an irreversible deposition of momentum to the ambient fluid. IGWs are an important mechanism for transporting energy and momentum in the atmosphere. If upward-propagating waves are incident upon a retrograde background wind jet, linear theory predicts that the waves can partially transmit through the jet. The amplitude of the transmitted waves grows exponentially with height due to anelastic effects, inducing a mean flow that ultimately drives the waves to break turbulently. In this talk, I will describe three-dimensional atmospheric IGW packets and their wave-induced mean flow, and define a transmission coefficient based on pseudomomentum. Using fully nonlinear numerical simulations, I will quantify wave packet transmission across retrograde jets modelling the eastward and westward phases of the Quasi-Biennial Oscillation. I will assess the extent to which the wave-induced mean flow enhances pseudomomentum transmission compared to the predictions of linear theory.
This event is part of the NSERC CREATE-funded Quantitative Climate Science summer school. More information about this initiative can be found at https://qcs-create2024.github.io/
