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SUMMARY:Leaky lid: new dissipative modes in the troposphere - Chumakova\, 
 L (University of Edinburgh)
DTSTART:20131203T113000Z
DTEND:20131203T121500Z
UID:TALK49148@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Much of our understanding of tropospheric dynamics is based on
  the concept of discrete internal modes. Internal gravity waves\, such as 
 those associated with convective systems\, propagate at definite speeds\, 
 typically associated with the first to third baroclinic vertical modes. Th
 ese waves are the dynamical backbone of the tropospheric dynamics\, even t
 hough their nature and speed can be altered significantly by nonlinearity\
 , moist convection\, mean wind shear\, etc. These discrete modes are a sig
 nature of systems of finite extent\, and are derived in a case when the at
 mosphere is bounded above by a rigid lid. In reality\, the atmosphere does
  not have a definite top\, and\, some argue\, should be modeled as semi-in
 finite\, leading to a continuous spectrum. Are the discrete rigid lid mode
 s then just a fallacy of overly simplified theoretical models? We present 
 a correction to the rigid lid by using a boundary condition at the top of 
 the troposphere\, that allows for a fraction of waves to escape to the str
 atosphere. The new discrete ``leaky modes decay with characteristic time-s
 cales\, which are in the ballpark of many atmospheric phenomena. We presen
 t both the non-rotating and rotating cases. \n\n
LOCATION:Seminar Room 1\, Newton Institute
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