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SUMMARY:Simple mathematical models of jet stream variability - Laura Cope 
 (DAMTP\, Cambridge)
DTSTART:20191126T130000Z
DTEND:20191126T140000Z
UID:TALK129220@talks.cam.ac.uk
CONTACT:Chris Hamilton
DESCRIPTION:Zonal jets are strong and persistent east-west flows that aris
 e spontaneously in planetary atmospheres and oceans. They are ubiquitous\,
  with key examples including mid-latitude jets in the troposphere\, multip
 le jets in the Antarctic Circumpolar Current and flows on gaseous giant pl
 anets such as Jupiter and Saturn. Turbulent flows on a beta-plane lead to 
 the spontaneous formation and equilibration of persistent zonal jets. Howe
 ver\, the equilibrated jets are not steady and the nature of the time vari
 ability in the equilibrated phase is of interest both because of its relev
 ance to the behaviour of naturally occurring jet systems and for the insig
 hts it provides into the dynamical mechanisms operating in these systems. 
 I will discuss aspects of zonal jet variability using a framework of barot
 ropic beta-plane models. Using a generalization of the quasilinear approxi
 mation\, in which nonlinear interactions between eddies are neglected\, I 
 will explore using direct numerical simulations (DNS) a new type of variab
 ility in which jets systematically migrate either north or south\, spontan
 eously breaking symmetry. Furthermore\, I will discuss additional insights
  from direct statistical simulations (DSS) in which the flow statistics\, 
 truncated at second order in equal-time cumulants\, are solved for directl
 y.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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