C S I R O
Hal Gordon
CSIRO Atmospheric Research, Aspendale,
Australia
CSIRO Mk3 Climate Model: Tropical Aspects
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 …….
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
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
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)
OGCM Spin-up:1000 years (accelerated)10 years Relaxation (6 day) to Levitus T & SSurface 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.
Next:
A “warts and all” look at the Mk3 coupled model in the tropics.
1st: Annual mean stresses and surface currents
Zonal stress
Meridional stress
OGCM spin up
Coupled
Next: Zonally averaged heat and fresh water flux:
OGCM during spinup
AGCM before coupling
CGCM
Surface heat flux
Fresh water flux
Next: Ocean surface temperature and salinity responses:
Next: Pacific thermocline:
Levitus
OGCM Coupled
Annual mean temperature(upper 400m)
along equator in Pacific Ocean
T @150W (15S:15N)
Obs
OGCM Coupled
Tropical sea level pressure; Global rainfall:
Obs
Annual mean sea level pressure
Observed and Mk3 AGCM rainfall (DJF)
Observed and Mk3 coupled rainfall (DJF)
Observed and Mk3 AGCM rainfall (JJA)
Observed and Mk3 coupled rainfall (JJA)
Annual mean precipitable water content (PWC)
C S I R O
Observed and CSIRO modeled monthly rainfall over NE Australia
Months
J F M A M J J A S O N D
Rai
nfal
l (m
m/d
ay)
0
1
2
3
4
5
6
7
8
CSIRO GCMObservation
Nino3.4
CSIRO modeled and observed temperature anomalies over NINO3 region
NINO3 region: E. Pacific (150W-90W, 5N-5S)
Power spectrum of the modeled and observed Niño3.4 index (5% and 95% confidence levels and a”red-noise” fit are overlaid.)
C S I R O
• 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)
Summary of Mk3 results
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