Convectively Forced Gravity Wave Drag GWD C in the CFS and GFS

1. Convectively ForcedGravity Wave DragGWDCin the CFS and GFS Åke Johansson

2. ACKNOWLEDGEMENTS Hye-Yeong Chun Jong-Jin Baik In-Sun Song Suranjana Saha Shrinivas Moorthi Hua-Lu Pan Jordan Alpert Huug van den Dool Mark Iredell

3. OUTLINE • Theory by Chun and Baik 1998 • Parameterization proposed by Chun and Baik 1998 • Climate runs with CFS • Data Assimilation and Week-1 runs with GFS • Conclusions • Suggestions

4. Theory by Chun and Baik 1998

5. 2-Dimensional x-z Steady-state Non-rotating Hydrostatic Inviscid Boussinesq Linearized – Small perturbations U, N Constant with x and z 0 ; Orographic Forcing Convective Forcing

7. U = 15 m/s N = 0.007 s-1 Zb = 1.5 km Zt = 11 km a1 = 10 km a2 = 5 a1 To = 273 K Qo = 1 J/kg/s w u

10. F = -U M Fz = -Uz M

11. F = -U M M F

12. F = -U M M F H L

13. Parameterization proposed by Chun and Baik 1998

14. STEP 1

15. c1 c2 a1 = αΔx c1 = 1.41 c2 = - 0.38 α = 0.1

16. V Vct Essentially 1-dimensional in the horizontal plane

17. STEP 2

18. Wave breaking Reduction of Momentum Flux M F

19. Lindzen’s Saturation Hypothesis If Reduce wave amplitude so that Ri = ¼ Gives new reduced

20. Main Reasons for Wave braking Stress Reduction Momentum deposition • Critical levels • Low wind speeds • Low density

21. Climate runs with CFS SET22 T126L64

22. Yonsei Univ GCM 2001 4° x 5° ( lat x lon ) Δx ~ 445 Km 15 Layers Top a 1 hPa Perpetual July AMIP integrations for 360 days Last 90 day averages are considered With vs Without GWDC α = 0.4 Encouraging Results NCAR CCM3 2004 T42 Δx ~ 315 Km 18 Layers Top a 2.5 hPa Perpetual January and July AMIP integrations for 3 yrs Last 2 yrs averages are considered With vs Without GWDC α < 0.16 Encouraging Results

23. CFS Experiments T126L64 Δx ~ 106 Km Top at 0.2 hPa SET22 = Operational CFS + Several updates New Shortwave radiation: Hourly + RRTM1 Longwave Radiation: Hourly + RRTM Realistic CO2 Maximum-random cloud overlap ESMF 3.0.1 Enthalpy equation

24. Observational and Simulation Data Sets

25. Two GWDC Experiments Two different ways in which the momentum compensation within the cloud is distributed

26. CONTROL EXPERIMENT

31. QBO

37. CFS have no QBO

40. Extreme Negative and Positive Anomalies Stratospheric Polar Night Jet 1971-2000

43. GWDC EXPERIMENT

46. 3 2 1

49. DJF GWDC1 1/10 Contour interval

50. DJF GWDC1