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The Non-Local Scheme in CAM3

The Non-Local Scheme in CAM3. Michael A. Brunke. introduction. z. free atmosphere. h. outer layer. PBL. 0.1 h. surface layer. 0. introduction. z. free atmosphere. h. outer layer. PBL. 0.1 h. surface layer. 0. introduction. z. free atmosphere. h. outer layer. PBL. 0.1 h.

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The Non-Local Scheme in CAM3

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  1. The Non-Local Scheme in CAM3 Michael A. Brunke

  2. introduction z free atmosphere h outer layer PBL 0.1h surface layer 0

  3. introduction z free atmosphere h outer layer PBL 0.1h surface layer 0

  4. introduction z free atmosphere h outer layer PBL 0.1h surface layer 0

  5. input parameters potential temperature temperature specific humidity height above surface pressure wind speed surface wind stress surface SH flux surface constituent flux output parameters kinematic sfc. const. flux eddy diffusivities countergradient terms convective temp. excess convective hum. excess surface friction velocity Obukhov length PBL height input and output

  6. free atmosphere Kc (Holtslag and Boville 1993) Ri < 0 Ri > 0

  7. C F 5 2 free atmosphere Kc Ri < 0 Ri > 0

  8. determination of h h = z where Ri = Ricr = 0.3 (Vogelezang and Holtslag 1996)

  9. sensitivity of h formulation Zeng et al., 2004: Marine atmospheric boundary layer height over the Eastern Pacific: data analysis and model evaluation. J. Climate, 17, 4159-4170.

  10. C 3 F 0 8 2 determination of h h = z where Ri = Ricr = 0.3

  11. determination of Kc

  12. determination of Kc

  13. turbulent velocity scales z / L < 0 0 z / L 1 z / L> 1

  14. turbulent velocity scales z / L < 0 0 z / L 1 z / L> 1

  15. turbulent velocity scales z / L < 0 0 z / L 1 z / L> 1 C 8 F 0 16 2

  16. turbulent velocity scales z / L < 0 0 z / L 1 z / L> 1 C 8 F 6 16 8

  17. countergradient term

  18. countergradient term C 1 F 0 17 8

  19. scheme sensitivity Tested sensitivity to choices for: • Ricr • b • b • a

  20. +25% +10% -10% -25% h Km Kh gh

  21. +25% +10% -10% -25% h Km Kh gh

  22. h Km Kh gh

  23. +25% +10% -10% -25% h Km Kh gh

  24. +25% +10% -10% -25% h Km Kh gh

  25. look-up table? • Not much value added by a LUT. • Simple formulation • Module runs very quickly. • Pull h’s from a LUT? • Model run to get LUT values could be run at L31.

  26. summary • CAM3 uses standard non-local turbulence scheme in PBL. • 17 tunable constants and 8 arbitrary functions. • Scheme not sensitive to Ricr and ; are sensitive to b and a • Convective temperature excess is needed. • LUT probably not necessary except maybe to get h.

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