Hal Gordon

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CSIRO Mk3 Climate Model Tropical Aspects

• Hal Gordon
• CSIRO Atmospheric Research, Aspendale,
• Australia

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CSIRO Mk3 Model

• Atmosphere
• Grid T63 (1.880 x 1.880)
• 18 levels - hybrid ?,p
• Semi-Lagrangian moisture transport
• UKMO convection (Gregory Rowntree)
• Liquid water clouds (Rotstayn)
• Dissipation ? Heating
• plus .

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CSIRO Mk3 Model

• Land surface
• Soil model - 6 levels
• Temperature, water, ice
• 9 soil types
• 13 land surface and/or vegetation types
• Snow-cover model - 3 layers
• Sea ice
• Flato-Hibler rheology
• Semtner thermodynamics (3 level)
• Variable leads lateral ice growth

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CSIRO Mk3 Model

• Ocean
• GFDL MOM 2.2
• Grid 0.940NS x 1.880EW (AGCM 1.880x1.880)
• 31 levels (10m surface ? 400m deep ocean)
• Shear mixing Integer Power Ri
• Surface mixing Bulk Ri
• Griffies et al. (1999) isoneutral mixing
• Griffies (1999) skew diffusion for GM90
• Quick third-order advection
• Penetrating solar / Jerlov(1977) water types
• No flux adjustment

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Mk 3 Computational Requirements

• Integration on NEC SX5
• About 1 model year per day using 4 processors
• Data storage per model year 1.2Gb approx.
• Reference Gordon et al. (2002) CSIRO Atmos.
  Res. Tech. Paper 60 (www.dar.csiro.au)

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OGCM Spin-up 1000 years (accelerated) 10 years
Relaxation (6 day) to Levitus T S Surface
stresses from AGCM AGCM Spin-up 120
years. Coupled Mk3 model Synchronous
coupling. Initial states from Spin-ups
above. Instant coupling - some adjustment to be
expected.
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Next A warts and all look at the Mk3 coupled
model in the tropics.
1st Annual mean stresses and surface currents
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Zonal stress
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Meridional stress
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OGCM spin up
Coupled
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Next Zonally averaged heat and fresh water
flux OGCM during spinup AGCM before
coupling CGCM
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Surface heat flux
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Fresh water flux
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Next Ocean surface temperature and salinity
responses
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Next Pacific thermocline
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Annual mean temperature (upper 400m) along
equator in Pacific Ocean
Levitus
OGCM
Coupled
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Obs
T _at_150W (15S15N)
OGCM
Coupled
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Tropical sea level pressure Global rainfall
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Annual mean sea level pressure
Obs
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Observed and Mk3 AGCM rainfall (DJF)
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Observed and Mk3 coupled rainfall (DJF)
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Observed and Mk3 AGCM rainfall (JJA)
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Observed and Mk3 coupled rainfall (JJA)
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Annual mean precipitable water content (PWC)
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Observed and CSIRO modeled monthly rainfall over
NE Australia
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Nino3.4
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CSIRO modeled and observed temperature anomalies
over NINO3 region
NINO3 region E. Pacific (150W-90W, 5N-5S)
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Power spectrum of the modeled and observed
Niño3.4 index (5 and 95 confidence levels and
ared-noise fit are overlaid.)
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Summary of Mk3 results

• Excessive cold tongue is evident in the OGCM
  spin-up
• It amplifies on coupling, extending west
• Tropical stresses look reasonable - but?
• Tropical heat flux less so (AGCM CGCM)
• Fresh water flux seems ok
• Rainfall split by cold tongue (coupled)
• Nino3.4 SST anomalies of correct() magnitude
• Issues - Drift - North Atlantic
  behaviour (Gulf Stream) - Tropical
  Pacific climatology (e.g., excessive
  penetration of cold tongue)

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Some actual words (truth) from the Minister for
Information, Mohammed Saeed Al-Sahaf (Comical
Ali ),being skeptical as ever,even about
climate modelling

• How good are current climate models?
• I now inform you that you are too far from
  reality.
• How far from reality around Baghdad?
• "They're not even within 100 miles. They are
  not in any place. They hold no place in Iraq.
• What about Middle East climate change?
• This is an illusion ... they are trying to
  sell to the others an illusion.
• Finally, are you worried about the Pacific cold
  tongue?
• "No, I am not scared and neither should you
  be!"

End