Gws in Ultra-fine Resolution Global Atmospheric Models

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Gws in Ultra-fine Resolution Global Atmospheric
Models
Thanks to GFDL-SKYHI model folks
J. Mahlman, J. Wilson, R. Hemler, L.
Umscheid.. AFES folks W. Ohfuchi et al. And
particularly to Li Yuan (now at Chase-Manhattan
Bank) John Koshyk (now at Toronto-Dominion
bank) Yoshiyuki Takahashi (Hokkaido U.)
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"Ultra-fine" AGCM

• GFDL SKYHI N270-L40 (T450)
• AFES T1279-L96 T639-L48, T639-L24
• NASA fvGCM N720-L48
• NICAM 3.5 km Icosahedral-L54

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"Ultra-fine" AGCM

• GFDL SKYHI N270-L40 (T450)
• AFES T1279-L96 T639-L48, T639-L24
• NASA fvGCM N720-L48
• NICAM 3.5 km Icosahedral-L54

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SKYHI Model

• Global, hydrostatic primitive equations
• A-grid-point model, explicit time-marching
• Model domain surface-about 80 km
• Ri-dependent vertical mixing
• Smagorinsky-type harmonic horizontal mixing
• Moist convective adjustment

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possible caveats

• A-grid - poor representation of dispersion
  relation for short waves, no enstrophy
  conservation - accumulation of energy ...?
• Interpolation needed for spherical harmonic
  expansions
• Moist convective adjustment
• Smagorinsky diffusion

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AFES Model

• Global, hydrostatic primitive equations
• Spectral model, semi-implicit time differencing
• Model domain surface to about 55 km
• Linear biharmonic diffusion
• Emanuel convection, Modified AS ... others

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Dry-dynamical-core Model

• No latent heat
• No thermal interaction with surface
• No topography
• Thermal forcing only through a Newtonian cooling
  towards a specified radiative equilibrium which
  is a function of pressure and latitude (following
  Held Suarez, 1994)

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(Nontopographic) Gravity Wave Forcing

• Can we characterize gravity wave fluxes into the
  stratosphere in terms of tropospheric
  circulations?
• e.g. how much spatial and temporal variability
  is in the flux (e.g. "90 of flux from 1 of the
  globe?")

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• Topographic drag - comparing detailed simulation
  with parameterization
• Review Garner 2005 JAS
• Earlier simulations e.g. Olaffson
  and
  Bougeault 1996, 1997
• Relation of near tropopause gravity wave fluxes
  to underlying dry dynamics (Dunkerton and
  Sullivan, 1992 Zhang 2004)