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SUMMARY:The Icosahedral Nonhydrostatic (ICON) model: formulation of the dy
 namical core and physics-dynamics coupling - Gnther Zngl\,   (Deutscher We
 tterdienst (DWD))
DTSTART:20120928T080000Z
DTEND:20120928T082500Z
UID:TALK40249@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:The nonhydrostatic dynamical core of the ICON model is formula
 ted on an icosahedral-triangular C-grid and uses the edge-normal wind comp
 onent\, the vertical wind speed\, density and virtual potential temperatur
 e as prognostic variables. In the vertical\, a generalized terrain-followi
 ng coordinate based on height is used that allows for a rapid decay with h
 eight of topographic structures\, thereby reducing the numerical discretiz
 ation errors over steep mountains. Moreover\, a truly horizontal formulati
 on of the horizontal pressure gradient term is used that greatly improves 
 numerical stability over steep mountains. The spatial discretizations are 
 second-order\, with some slight degradation near the pentagon points of th
 e basic icosahedron\, and are primarily optimized for computational effici
 ency\, ensuring strict mass conservation and consistent tracer transport b
 ut no exact conservation of energy or vorticity-related quantities. Time i
 ntegration is based on a second-order predictor-corrector scheme that is f
 ully explicit in the horizontal and implicit for the terms entering into v
 ertical sound wave propagation. The dynamics time step is therefore limite
 d by the CFL stability condition for horizontal sound wave propagation\, b
 ut a longer time step (typically 4x or 5x) is used for tracer transport an
 d fast-physics parameterizations. A important aspect of physics-dynamics c
 oupling is that all terms related to latent heat release have to be conver
 ted into temperature changes at constant volume because density is used as
  a prognostic variable and is kept fixed during the physics call. \n\n
LOCATION:Seminar Room 1\, Newton Institute
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