cloud feedbacks in echam5: preparatory results for cmip5 daniel klocke johannes quaas, marco...
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Cloud feedbacks in ECHAM5: preparatory
results for CMIP5
Daniel Klocke
Johannes Quaas, Marco Giorgetta
Max-Planck-Institut für MeteorologieKlimaCampus, Hamburg
Overview
• PRP – Method– Temporal variability– Geographical distribution– PDFs of feedback factors
• Gregory – Method
Method
• Two T31L19 slab-ocean simulations (CTRL/2xCO2).• Single column radiation code run on 6 hr output.• Recalculate radiative fluxes and exchange parameters
of interest:F
rom 2CO
2
to CTRL (Forward, FW)
From CTRL to 2CO
2
(Backward, BW)
• Partial radiative perturbation (PRP) method:
λ = Feedback factorR = Radiative forcing (net TOA radiative fluxes) Ts = Surface temperaturex = replaced variable (clouds, water vapor, temperature, surface albedo)
Method • Variability • Distribution • PDFs • Gregory
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
Temporal variability
Global six hourly mean feedback factors [W m-2 K-1]
Cloud long wave0.9
-0.3
Cloud short wave
-6.0
6.0
-6.0
6.0 Cloud net
Method • Variability • Distribution • PDFs • Gregory
Geographical distributionSurface albedo Water vapor
PlanckLapse rate -5 50
Method • Variability • Distribution • PDFs • Gregory
Δ total cloud cover [%] Δ vertically integratedcloud ice [kg m-2]
Δ vertically integratedcloud water [kg m-2]
Geographical distributionNet cloud feedback factor
-5 50
Method • Variability • Distribution • PDFs • Gregory
Net cloud feedback factor
Short wave component Long wave component-5 50
Method • Variability • Distribution • PDFs • Gregory
Geographical distribution
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
Gregory Method
NetClear sky short waveClear sky long waveClouds short waveClouds 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 / 4.05Sensitivity (experiment): 2.98 K
Gregory Method
NetClear sky short waveClear sky long waveClouds short waveClouds long wave
Method • Variability • Distribution • PDFs • Gregory
ΔCRF/ΔT PRP Greg Greg Exp-0.11 0.16 0.01 -0.42
-0.24 0.17 0.07 0.19
-0.35 0.34 0.08 -0.23
Short wave
Long wave
Net
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.
Method • Variability • Distribution • PDFs • Gregory
Soden and Held, 2006adapted
PRP - six years
ΔCRF/ΔT - six years