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SUMMARY:Spontaneous gravity wave radiation from nearly balanced rotational
  flows in a shallow water system - Sugimoto\, N (Keio)
DTSTART:20081209T120000Z
DTEND:20081209T123000Z
UID:TALK15600@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Spontaneous gravity wave radiation from nearly balanced rotati
 onal flows is investigated in shallow water system on a rotating sphere. G
 ravity waves are very important for their role on global material circulat
 ion in the middle atmosphere. It is suggested that gravity waves are radia
 ted from strong rotational flows\, such as polar night jet\, sub-tropical 
 jet\, and typhoon in recent observational studies. This radiation process 
 is called as a spontaneous gravity wave radiation\, since gravity waves ar
 e spontaneously radiated from initial balanced rotational flows. Although 
 there are several numerical studies\, this process has not been fully unde
 rstood. In the present study\, we use the most simplified system of shallo
 w water that includes both gravity waves and rotational flows. In addition
 \, the spectral-like three point combined compact difference (sp-CCD) sche
 me is used\, which has high accuracy as well as the spherical harmonics mo
 del. This model allows us to estimate gravity wave amplitude with high acc
 uracy. We investigate dependencies of positions of the jet on spontaneous 
 gravity wave radiation. To discuss on the conditions of gravity wave radia
 tion and propagation\, we use the analogy with the theory of the aero-acou
 stic sound wave radiation (Lighthill theory). We also show results of two 
 layer shallow water system in which small internal gravity waves are spont
 aneously radiated from baloclinic instability. Finally\, we will mention r
 ecent theoretical study of spontaneous gravity wave radiation from simple 
 vortex pairs.
LOCATION:Seminar Room 1\, Newton Institute
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