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CSIRO Mk3 Climate Model: Tropical Aspects

CSIRO Mk3 Climate Model: Tropical Aspects. Hal Gordon CSIRO Atmospheric Research, Aspendale , Australia. CSIRO Mk3 Model. • Atmosphere Grid: T63 (1.88 0 x 1.88 0 ) 18 levels - hybrid ,p Semi-Lagrangian moisture transport UKMO convection (Gregory & Rowntree)

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CSIRO Mk3 Climate Model: Tropical Aspects

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  1. CSIRO Mk3 Climate Model: Tropical Aspects Hal Gordon CSIRO Atmospheric Research, Aspendale, Australia

  2. 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 …….

  3. 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

  4. 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

  5. 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)

  6. 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.

  7. Next: A “warts and all” look at the Mk3 coupled model in the tropics. 1st: Annual mean stresses and surface currents

  8. Zonal stress

  9. Meridional stress

  10. OGCM spin up Coupled

  11. Next: Zonally averaged heat and fresh water flux: OGCM during spinup AGCM before coupling CGCM

  12. Surface heat flux

  13. Fresh water flux

  14. Next: Ocean surface temperature and salinity responses:

  15. Next: Pacific thermocline:

  16. Annual mean temperature (upper 400m) along equator in Pacific Ocean Levitus OGCM Coupled

  17. Obs T @150W (15S:15N) OGCM Coupled

  18. Tropical sea level pressure; Global rainfall:

  19. Annual mean sea level pressure Obs

  20. Observed and Mk3 AGCM rainfall (DJF)

  21. Observed and Mk3 coupled rainfall (DJF)

  22. Observed and Mk3 AGCM rainfall (JJA)

  23. Observed and Mk3 coupled rainfall (JJA)

  24. Annual mean precipitable water content (PWC)

  25. Observed and CSIRO modeled monthly rainfall over NE Australia

  26. Nino3.4

  27. CSIRO modeled and observed temperature anomalies over NINO3 region NINO3 region: E. Pacific (150W-90W, 5N-5S)

  28. Power spectrum of the modeled and observed Niño3.4 index (5% and 95% confidence levels and a”red-noise” fit are overlaid.)

  29. 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)

  30. 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

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