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Cloud feedbacks in ECHAM5: preparatory results for CMIP5

Cloud feedbacks in ECHAM5: preparatory results for CMIP5. Daniel Klocke Johannes Quaas, Marco Giorgetta. Max-Planck-Institut für Meteorologie KlimaCampus, Hamburg. Overview. PRP – Method Temporal variability Geographical distribution PDFs of feedback factors Gregory – Method. Method.

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Cloud feedbacks in ECHAM5: preparatory results for CMIP5

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

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

  3. Method • Partial radiative perturbation (PRP) method: λ = Feedback factor R = Radiative forcing (net TOA radiative fluxes) Ts = Surface temperature x = replaced variable (clouds, water vapor, temperature, surface albedo) • Two T31L19 slab-ocean simulations (CTRL/2xCO2). • Single column radiation code run on 6 hr output. • Recalculate radiative fluxes and exchange parameters of interest: • From 2CO2 to CTRL (Forward, FW) • From CTRL to 2CO2 (Backward, BW) Method • Variability • Distribution • PDFs • Gregory

  4. Method In other words… CTRL-World 2CO2-World Method • Variability • Distribution • PDFs • Gregory

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

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

  7. Soden and Held, 2006 Method • Variability • Distribution • PDFs • Gregory

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

  9. Geographical distribution Water vapor Surface albedo -5 0 5 Lapse rate Planck Method • Variability • Distribution • PDFs • Gregory

  10. Geographical distribution Net cloud feedback factor 0 -5 5 Δ vertically integratedcloud water [kg m-2] Δ vertically integrated cloud ice [kg m-2] Δ total cloud cover [%] Method • Variability • Distribution • PDFs • Gregory

  11. Geographical distribution Net cloud feedback factor 0 -5 5 Long wave component Short wave component Method • Variability • Distribution • PDFs • Gregory

  12. PDFs of feedback factors BW x (-1) - FW • 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 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 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 Method • Variability • Distribution • PDFs • Gregory

  15. Gregory Method Net Clear sky short wave Clear sky long wave Clouds short wave Clouds long wave Short wave Long wave Net Method • Variability • Distribution • PDFs • Gregory

  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 6.0 6.0 -6.0 -6.0 Method • Variability • Distribution • PDFs • Gregory

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

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

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