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CATEGORIES:DAMTP Atmosphere-Ocean Dynamics
SUMMARY:Balance model for equatorial long waves - Ian Chan
  (University of Toronto)
DTSTART;TZID=Europe/London:20131017T130000
DTEND;TZID=Europe/London:20131017T140000
UID:TALK48319AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/48319
DESCRIPTION:When a dynamical system admits both fast and slow 
 timescale dynamics\, a\nsimplified model can be co
 nstructed by systematically filtering out the\nfas
 t dynamics. In the context of atmospheric dynamics
 \, these models are\ncalled balance models\, with 
 the quasi-geostrophic (QG) model being the\nmost n
 otable example. Although the QG model is immensely
  useful for the\nmidlatitudes\, it is not applicab
 le to the tropics as a singularity\ndevelops. Prev
 ious attempts at deriving equatorial balance model
 s have\nbeen unsuccessful as they filter out Kelvi
 n waves\, which play a dominant\nrole in equatoria
 l dynamics. In this talk I will demonstrate how a\
 nmodified asymptotic approach can be used to syste
 matically derive\nequatorial balance models in the
  planetary scale regime\, which capture\nslow Ross
 by and Kelvin wave modes while filtering out fast 
 gravity wave\nmotions. The expansion is based on t
 he smallness of the ratio of\nmeridional to zonal 
 scales\, which can also be interpreted as a\nsepar
 ation in timescale. Both the adiabatic and the dia
 batic (forced)\ncase are considered. An interestin
 g result is that even though the\nleading order ba
 lance dynamics fails in the isotropic regime\, the
 \nbalance relations remain accurate\; this suggest
 s that the balance\nrelations can potentially be u
 seful in applications such as data\nassimilation.
LOCATION:MR5\, Centre for Mathematical Sciences
CONTACT:
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