1. Cloud feedbacks in ECHAM5: preparatory results for CMIP5 Daniel Klocke Johannes Quaas, Marco Giorgetta Max-Planck-Institut für Meteorologie KlimaCampus, Hamburg

2. Overview PRP – Method – Temporal variability – Geographical distribution – PDFs of feedback factors Gregory – Method

3. Method Two T31L19 slab-ocean simulations (CTRL/2xCO 2 ). Single column radiation code run on 6 hr output. Recalculate radiative fluxes and exchange parameters of interest: From 2CO 2 to CTRL (Forward, FW) From CTRL to 2CO 2 (Backward, BW) Partial radiative perturbation (PRP) method: λ = Feedback factor R = Radiative forcing (net TOA radiative fluxes) T s = Surface temperature x = replaced variable (clouds, water vapor, temperature, surface albedo) Method Variability Distribution PDFs Gregory

4. Method In other words… CTRL-World2CO 2 -World Method Variability Distribution PDFs Gregory

5. Temporal variability Surface albedo Lapse rate Planck Water vapor Global six hourly mean feedback factors [W m -2 K -1 ] 1.0 -0.2 0.3 -1.5 -3.0 -6.0 2.4 1.2 Method Variability Distribution PDFs Gregory

6. Temporal variability Global six hourly mean feedback factors [W m -2 K -1 ] Cloud long wave 0.9 -0.3 Cloud short wave -6.0 6.0 -6.0 6.0 Cloud net Method Variability Distribution PDFs Gregory

7. Soden and Held, 2006

8. Method Variability Distribution PDFs Gregory Soden and Held, 2006 adapted PRP - six years

9. Geographical distribution Surface albedo Water vapor PlanckLapse rate -550 Method Variability Distribution PDFs Gregory

10. Δ total cloud cover [%] Δ vertically integrated cloud ice [kg m -2 ] Δ vertically integrated cloud water [kg m -2 ] Geographical distribution Net cloud feedback factor -55 0 Method Variability Distribution PDFs Gregory

11. Net cloud feedback factor Short wave component Long wave component -55 0 Method Variability Distribution PDFs Gregory Geographical distribution

12. PDFs of feedback factors Blue: PRP-Forward (Bin 0.1 W m -2 K -1 ) Red: PRP-Backward Shaded area between min and max of six years Dark lines: Average of six years BW x (-1) - FW Method Variability Distribution PDFs Gregory

13. PDFs of cloud feedback Method Variability Distribution PDFs Gregory

14. Gregory Method Net Clear sky short wave Clear sky long wave Clouds short wave Clouds long wave Method Variability Distribution PDFs Gregory Stratospheric adjusted radiative forcing (Gregory): 3.91 W m -2 / 4.12 W m -2 Stratospheric adjusted radiative forcing (experiment): 3.87 W m -2 Sensitivity (Gregory): 3.24 K / 4.05 Sensitivity (experiment): 2.98 K

15. Gregory Method Net Clear sky short wave Clear sky long wave Clouds short wave Clouds long wave Method Variability Distribution PDFs Gregory ΔCRF/ΔTPRPGregGreg Exp -0.110.160.01-0.42 -0.240.170.070.19 -0.350.340.08-0.23 Short wave Long wave Net

16. Conclusion Cloud, Planck, water vapor, lapse rate and albedo feedback factors calculated using a single column radiation model with the PRP method for several years. The temporal variability of the cloud feedback factor is very large. This is due to a high variability of the short wave component. The cloud feedback is regionally strongest in the solar spectra, but on global scale of the same magnitude as the LW cloud feedback. The global patterns are dominated by the SW cloud feedback factor. PDFs of Planck, lapse rate and long wave cloud feedback factor show a clear shift in the distribution, mainly due to ‘decorrelation perturbations’ and masking effects The Gregory method gives comparable results, especially for the stratospheric adjusted radiative forcing, the sensitivity and the long wave component of the cloud feedback.

17. Traditional Method Method Variability Distribution PDFs Gregory -6.0 6.0 -6.0 6.0

18. Method Variability Distribution PDFs Gregory Soden and Held, 2006 adapted PRP - six years ΔCRF/ΔT - six years

19. trad0 = -1.703 -0.516 -1.353 -0.695 -0.537 -1.459