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SUMMARY:The leapfrog is dead.  Long live the leapfrog! - Williams\, P (Uni
 versity of Reading)
DTSTART:20120917T123000Z
DTEND:20120917T130000Z
UID:TALK39817@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:The centred-difference time-stepping scheme\, known affectiona
 tely as the leapfrog scheme\, has been used widely in atmosphere and ocean
  models for over 40 years. However\, the numerical dissipation and loss of
  accuracy associated with the Robert-Asselin filter (which is used to cont
 rol the computational mode) are becoming unacceptable to some modellers\, 
 who are starting to turn to schemes that are less dissipative and more acc
 urate.\n \nThis talk will argue that there is still plenty of life left in
  the leapfrog. I will describe some simple and computationally inexpensive
  strategies to improve it\, including the replacement of the Robert-Asseli
 n filter with the RAW filter. The methods reduce the numerical dissipation
  and increase the accuracy\, whilst retaining the stability of the physica
 l mode and effectively controlling the computational mode. Examples will b
 e shown of recent implementations of these methods in several models\, lea
 ding to improvements in the simulation skill.\n \n
LOCATION:Seminar Room 2\, Newton Institute Gatehouse
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