BEGIN:VCALENDAR VERSION:2.0 PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4// BEGIN:VEVENT UID:20250731T203421EDT-7687h3rsum@132.216.98.100 DTSTAMP:20250801T003421Z DESCRIPTION:Atmospheric and Oceanic Sciences Departmental Seminar Series\n \npresents\n\nPeriodicity disruption of a model quasi-biennial oscillation \n\na talk by\n\nLouis-Philippe Nadeau\n ProfessorInstitut des sciences de la mer de Rimouski\,\n Université du Québec à Rimouski\, Québec\n\nThe quas i-biennial oscillation (QBO) of equatorial winds on Earth is the clearest example of the spontaneous emergence of a periodic phenomenon in geophysic al fluids. In recent years\, observations have revealed intriguing disrupt ions of this regular behavior\, and different QBO-like regimes have been r eported in a variety of systems. The non-periodic nature of the reversals has been interpreted as the system's response to transient external variat ions. Here we show that part of the variability could be attributed to the intrinsic dynamics of wave-mean flow interactions in stratified fluids.\n \nUsing a constant-in-time monochromatic wave forcing\, we explore the int rinsic variability of a hierarchy of simplified models of the QBO\, rangin g from a quasilinear model to fully nonlinear simulations. The existence o f new bifurcations associated with faster and shallower flow reversals\, a s well as a quasiperiodic route to chaos are reported in these models.\n\n Then\, focusing on the regular QBO-like regime\, we investigate how the pr oximity to a bifurcation point influences the resilience of a given oscill ation to external variability by considering the effect of a time-dependen t perturbation superimposed on its reference monochromatic wave forcing. W e show that perturbations of the oscillation are widely amplified in the p roximity of bifurcation points occurring in the phase space of these model s\, thus suggesting that intrinsic dynamics may be equally influential as external variability in explaining disruptions of this regular behavior.\n \nMonday Nov 04/ 3:30 PM/ Burnside Hall/ Room 934\n DTSTART:20191104T203000Z DTEND:20191104T220000Z LOCATION:Room 934 SUMMARY:Periodicity disruption of a model quasi-biennial oscillation URL:/meteo/channels/event/periodicity-disruption-model -quasi-biennial-oscillation-302019 END:VEVENT END:VCALENDAR