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SUMMARY:ICON-IAP: A non-hydrostatic global model designed for energetic co
 nsistency - Almut Gassmann\,   (Leibniz-Institut fr Atmosphrenphysik\, Khl
 ungsborn)
DTSTART:20120927T135000Z
DTEND:20120927T141500Z
UID:TALK40224@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:The talk describes a new global non-hydrostatic dynamical core
  (ICON-IAP: Icosahedral Nonhydrostatic model at the Institute for Atmosphe
 ric Physics) on a hexagonal C-grid which is designed to conserve mass and 
 energy. Energy conservation is achieved by discretising the antisymmetric 
 Poisson bracket which mimics correct energy conversions between the differ
 ent kinds of energy (kinetic\, potential\, internal). Because of the brack
 et structure this is even possible in a complicated numerical environment 
 with (i) the occurrence of terrain-following coordinates with all the metr
 ic terms in it\, (ii) the horizontal C-grid staggering on the Voronoi-mesh
  and the complications induced by the need for an acceptable stationary ge
 ostrophic mode\, and (iii) the necessity for avoiding the Hollingsworth-in
 stability. The model is equipped with a Smagorinsky-type nonlinear horizon
 tal diffusion. The associated dissipative heating is accounted for by the 
 application of the discrete product rule for derivatives. The time integra
 tion scheme is explicit in the horizontal and implicit in the vertical. In
  order to ensure energy conservation\, the Exner pressure has to be off-ce
 ntered in the vertical velocity equation and extrapolated in the horizonta
 l velocity equation. \n\nTest simulations are performed for small scale an
 d global scale flows. A test simulation of linear nonhydrostatic flow over
  a rough mountain range shows the theoretically expected gravity wave prop
 agation. The baroclinic wave test is extended to 40 days in order to check
  the Lorenz energy cycle. The model exhibits excellent energy conservation
  properties even in this strongly nonlinear and dissipative case. The Held
 -Suarez test confirms the reliability of the model over even longer timesc
 ales.\n\n
LOCATION:Seminar Room 1\, Newton Institute
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