university of washington department of atmospheric sciences
DESCRIPTION
The Response of the Southern Hemispheric Eddy-Driven Jet to Future Changes in Shortwave Radiation in CMIP5. Paulo Ceppi , Mark D. Zelinka and Dennis L. Hartmann Souther n Ocean Clouds Workshop , 18 March 2014. University of Washington Department of Atmospheric Sciences. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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The Response of the Southern Hemispheric Eddy-Driven Jet to Future Changes in Shortwave Radiation in CMIP5
University of WashingtonDepartment of Atmospheric Sciences
Paulo Ceppi, Mark D. Zelinka and Dennis L. Hartmann Southern Ocean Clouds Workshop, 18 March 2014
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Outline• Changes in shortwave radiation in
RCP8.5• Impact of SW changes on SSTs and
midlatitude jet• Determining causal relationships• Conclusions
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Absorbed SW radiation (ASR)2050-2099 minus 1950-1999, in W m-2
AS
R c
hang
e (W
m-2)
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ASR changes (in W m-2)A
SR
cha
nge
(W m
-2)
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ASR changes (in W m-2)albedo
AS
R c
hang
e (W
m-2)
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ASR changes (in W m-2)albedo clouds
AS
R c
hang
e (W
m-2)
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Absorbed SW radiation (ASR)
• considerable inter-model spread• wide variety of meridional gradients
of ASR response
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Effect of ASR changes• Atmospheric circulation is very
sensitive to meridional SST gradient• Idea: can the different ASR
gradient responses explain spread in SST and eddy-driven jet response?
• Define simple ASR and SST gradient indices
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Change in ASR gradientASR index = <ASR>20-50 – <ASR>50-90
AS
R c
hang
e (W
m-2)
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ASR index vs Tsfc index
change in ASR gradient change in SST gradient
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ASR index vs jet shift
increase in ASR/SST gradient poleward jet shift
poleward jet shift
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ASR index vs jet shift
But wait! What if the jet shifts are causing the different ASR responses?
poleward jet shift
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Causality
• To solve this, use AMIP + AMIPfuture experiments (11 models)
• AMIP: 1979–2005 SSTs• AMIPfuture: AMIP SSTs + patterned anomaly• prescribed SSTs = SW effects are suppressed
jet shift cloud shift SST anomalies1
2
cloud response SST anomalies jet shift
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Causality
• If no relationship between ASR and jet shift in AMIPfuture
• If jet shift and ASR changes are related
jet shift cloud shift SST anomaliescloud response SST anomalies jet shift1
2
In AMIPfuture:
1
2
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jet shift vs ASR indexRCP8.5
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jet shift vs ASR indexRCP8.5
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jet shift vs ASR indexRCP8.5 + AMIPfutureRCP8.5
no relationship between jet shift and ASR change in AMIPfuture
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cloud response SST anomalies jet shift
ASR changes: AMIP vs RCP8.5
SW changes are the same! (despite different jet shifts)
jet shift cloud shift ASR/SST anomalies12
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ASR response to natural jet variability (in W m-2)
AS
R re
spon
se (W
m-2)
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ASR response to natural jet variability (in W m-2)
jet shift cloud shift ASR/SST anomalies2
AS
R re
spon
se (W
m-2)
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Conclusions• Large spread in ASR changes in
RCP8.5• ASR changes cause spread in SST
gradient change and jet shift• Spread in ASR response due to
model-dependent sensitivity to SST warming
• Poleward jet shift seems to play a minor role in ASR responseThe End Thank you!
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Extra plots
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ASR changes in AMIPfuture2050-2099 minus 1950-1999, in W m-2 K-1
AS
R c
hang
e (W
m-2)
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Effect of clouds2050-2099 minus 1950-1999
AS
R c
hang
e (W
m-2)
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Effect of surface albedo2050-2099 minus 1950-1999
sea ice
AS
R c
hang
e (W
m-2)
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jet s
hift
(deg
S K
-1)
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jet s
hift
(deg
S K
-1)