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

Method

In other words…

CTRL-World 2CO2-World

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

Method • Variability • Distribution • PDFs • Gregory

Soden and Held, 2006

Method • Variability • Distribution • PDFs • Gregory

Soden and Held, 2006adapted

PRP - six years

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

PDFs of cloud feedback

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.

Traditional Method

Method • Variability • Distribution • PDFs • Gregory

-6.0

6.0

-6.0

6.0

Method • Variability • Distribution • PDFs • Gregory

Soden and Held, 2006adapted

PRP - six years

ΔCRF/ΔT - six years

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