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