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SUMMARY:In search of strongly stratified turbulence - Colm-Cille Caufield 
 (University of Cambridge)
DTSTART:20240430T134500Z
DTEND:20240430T150000Z
UID:TALK216517@talks.cam.ac.uk
DESCRIPTION:Stratified flows are common place in geophysics\, and understa
 nding how such flows become and remain turbulent is a research area of maj
 or significance\, with&nbsp\;relevance to heat and pollutant transport ove
 r a huge range of scales. Parameterising such turbulence\, and its associa
 ted irreversible scalar mixing in terms of larger&nbsp\;scale flow paramet
 ers is needed to capture the key effects of turbulence in larger scale mod
 els of the earth&rsquo\;s (rapidly changing) climate system. Unfortunately
 \,&nbsp\;constructing reasonable and robust parameterisations is exception
 ally challenging\, not least because of the widely observed &nbsp\;tendenc
 y for sufficiently `strongly&rsquo\; stratified&nbsp\;flows to form (and m
 aintain) density staircases\, with relatively deep\, relatively well-mixed
  `layers&rsquo\; being separated by thinner `interfaces&rsquo\; of enhance
 d density gradient.&nbsp\;Here the initial `strength&rsquo\; of the strati
 fication is quantified in terms of the magnitude of the time scales and/or
  length scales of the background stratification relative to the&nbsp\;equi
 valent scales of the turbulence and/or a larger scale background flow\, an
 d traditionally it has been assumed that much of the world&rsquo\;s oceans
  can be considered to be&nbsp\;in a `strongly stratified turbulence&rsquo\
 ; regime\, with an associated predicted highly anisotropic flow dynamics.&
 nbsp\;\nUnfortunately\, the existence of such &nbsp\;spatio-temporally var
 iable `staircases&rsquo\; and layers calls into question the very concept 
 of a flow being `strongly&rsquo\; stratified\, due not&nbsp\;least to the 
 spatio-temporal variation of the relevant length scales and time scales. I
  will attempt to discuss various aspects of this interesting issue in term
 s of real-world&nbsp\;observations\, laboratory experiments and numerical 
 simulations.
LOCATION:Seminar Room 1\, Newton Institute
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