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SUMMARY:Jet formation in decaying two-dimensional turbulence on a rotating
  sphere - Yoden\, S (Kyoto)
DTSTART:20081209T160000Z
DTEND:20081209T163000Z
UID:TALK15622@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Jet formation in decaying two-dimensional turbulence on a rota
 ting sphere is reviewed from the view point of wave mean-flow interaction 
 for both shallow-water case and non-divergent case as the limit of Fr (Fro
 ude number) going to zero.\n\nA series of computations are performed to co
 nfirm the behavior of zonal mean zonal flow generation on the parameter sp
 ace of the rotation rate Omega and Fr. When the flow is non-divergent and 
 Omega is large\, intense retrograde circumpolar jets tend to emerge in add
 ition to a banded structure of mean zonal flows with alternating flow dire
 ctions. As Fr increases\, circumpolar jets disappear and a retrograde jet 
 emerges in the equatorial region.\n\nThe appearance of the intense retrogr
 ade jets can be understood by the angular momentum transport associated wi
 th the generation\, propagation\, and absorption of Rossby waves. When the
  flow is non-divergent\, long Rossby waves tend to be absorbed near the po
 les. In contrast\, when Fr is large\, Rossby waves can hardly propagate po
 leward and tend to be absorbed near the equator.\n\nThe direction of the e
 quatorial jet\, however\, is not always retrograde. Our ensemble experimen
 ts showed the emergence of a prograde jet\, though less likely. This resul
 t is contrasted with the previous studies that reported retrograde equator
 ial jets in all the cases for shallow-water turbulence. Furthermore\, a me
 an zonal flow induced by wave-wave interactions was examined using a weakl
 y nonlinear model to investigate the acceleration mechanisms of the equato
 rial jet. The second-order acceleration is induced by the Rossby and mixed
  Rossby-gravity waves and its mechanisms can be categorized into two types
 .
LOCATION:Seminar Room 1\, Newton Institute
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