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Biases in Ocean and Coupled General Circulation models

Biases in Ocean and Coupled General Circulation models. Gabriel A. Vecchi, Matthew Harrison, Andrew Wittenberg, Tony Rosati NOAA/GFDL, Princeton, NJ. From Thomas Reichler , U. Utah. GFDL SST Diffs with Levitus Annual Mean. GFDL - OM3 Horiz. Resolution - 1x.33

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Biases in Ocean and Coupled General Circulation models

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  1. Biases in Ocean and Coupled General Circulation models Gabriel A. Vecchi, Matthew Harrison, Andrew Wittenberg, Tony Rosati NOAA/GFDL, Princeton, NJ

  2. From Thomas Reichler , U. Utah

  3. GFDL SST Diffs with Levitus Annual Mean • GFDL - OM3 • Horiz. Resolution - 1x.33 • Vert. Resolution - 50 levels (21 levels in top 210m) Domain - Tropical Pacific only • Forcing - "Diurnal to Decadal Global Forcing For Ocean and Sea-Ice Models: The Data Sets and Flux Climatologies" W. Large, S. Yeager • Period -43 years (1958-2000)

  4. Effect of coupling From Wittenberg et al (2005)

  5. Mean SST Biases in Tropical Pacific NO COLD TONGUE NO WARM POOL

  6. Seasonal Cycle – Equatorial SST • In OGCM: • Amplitude of seasonal variations in SST weaker than obs. • Phasing better in EPIC region than 140W-110W.

  7. Coupled model evolution at 110W. From Wittenberg et al (2005)

  8. Seasonality of SST Biases in Eastern Tropical Pacific

  9. Currents Currents

  10. Currents From Wittenberg et al (2005)

  11. (lack of) TIWs in CM2 TMI SST

  12. (no) TIWs in other coupled models

  13. Only IPCC Coupled Model with Strong TIWs is flux-corrected one TMI SST

  14. So what? Mixed layer heating by horizontal advection from TIWs in 1/10deg OGCM • TIWs act to heat Equator. 150W-100W mixed layer heating by horizontal advection from TIWs in 1/10deg OGCM

  15. TIWs in forced OGCM OGCM Zonal Currents 0N, 140W.

  16. (no) TIWs with CM2 winds

  17. Remove anisotropic viscosity in coupled model

  18. OGCM heat transport from TIWs

  19. Sumary • GFDL OGCM exhibits cold-tongue cold bias, stratus region warm bias. • Biases strengthen and extend with coupling. • CGMS biases as or more different than they are similar – one/same cure? • CGCM biases vary seasonally. East Pac most cool in boreal spring. • TIWs missing from CGCMs – even though OGCM components have them. • Mixing? Winds? What is impact on SST biases? • What do we need to do to get NECC, shears?

  20. From Thomas Reichler , U. Utah

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