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ENSO simulation in MIROC: ENSO simulation in MIROC: Perspectives toward CMIP5Perspectives toward CMIP5
M. Watanabe1, M. Chikira2, Y. Imada1, M. Kimoto1
and MIROC modeling team
Watanabe et al. (2010, JC in press.)
CLIVAR ENSO WS, Nov 17-19, 2010
1: Atmosphere and Ocean Research Institute (AORI), The Univ. of Tokyo2: Research Institute for Global Change (RIGC), JAMSTEC, Japan
Motivation (or triggering)Motivation (or triggering)Obs.(ProjD_v6.7&ERA40) MIROC3. T42
Collins et al. (2010, Nature Geo.)
Improvements in an update (MIROC5)Improvements in an update (MIROC5)Obs.(ProjD_v6.7&ERA40) MIROC3. T42 MIROC3. T213 MIROC5. T85
impact of resolution
impact of new model physics
ENSO in CGCMsENSO in CGCMsENSO diversity in CMIP3 models -> Controlling ENSO in complex system is still challenging
ENSO diversity in CGCMs is likely due to the atm. component - Schneider 2002, Guilyardi et al. 2004, 2009
In particular, convection scheme potentially has a great impact
• CMT - Wittenberg et al. 2003, Kim et al. 2008, Neale et al. 2008
• Entrainment (incl. cumulus triggering) - Wu et al. 2007, Neale et al. 2008
• Low clouds - Toniazzo et al. 2008, Lloyd et al. 2009
Perturbing cumulus convectionsPerturbing cumulus convections
Efficiency of the entrainment controlled by large suppress deep clouds
2 ,
aB
w
2 2
2 (1 )w w
a Bz
exp Length
L500 0.5 85
L525 0.525 85
L550 0.55 85
L575 0.575 85 is the default value in the official T85 CTL
Sensitivity experiments w/ T42 MIROC5Sensitivity experiments w/ T42 MIROC5Sensitivity experiments w/ T42 MIROC5Sensitivity experiments w/ T42 MIROC5
Chikira and Sugiyama (2010, JAS)
Entrainment rate (Conventional A-S scheme: prescribedC-S scheme: state dependent
Chikira-Sugiyama convection scheme:Mixture of A-S and Gregory schemes A-SC-S
Vertical profiles of in a single column model
Cloud type
Alt
itud
e [
eta
]
ENSO in MIROC5ENSO in MIROC5
L500
L525
L550
L575
Reality?
artificial? CP El Niño?
Obs.
GCM
Comparison of the ENSO structure
As ENSO amplifies, maximum in both precipitation and x anomalies be stronger but shifted to the western Pacific -> reduction in the effective Bjerknes feedback
Precipitation
Zonal stress
Nino3-regression along EQ
longitude Lloyd et al. (2009)
N
ino3
SS
T S
td D
ev
L500L575
Mean state differencesMean state differences
SSTDeviations from the ensemble mean
precip.
L500
L525
L550
L575
EN
SO
amplitude
Larger (efficient cumulus entrainment) -> drier & colder mean state in E. Pacific <-> weaker ENSO
ENSO metric in MIROC5Cold tongue dryness (CTD) index
AGCM experiments (5yrs each)exp Remark
L500a 0.5
L525a 0.525
L550a 0.55
L575a 0.575
L500b 0.5 =0.575 over Nino3
L575b 0.575 =0.5 over ITCZ
SST & ice from CGCM ensemble mean Coupling always works to reduce the precipitation contrast
Direct effect of convection
Coupled feedbacks
Mechanism of convective Mechanism of convective control control
Dry cold tongue -> reduced effective Bjerknes feedback
Wet cold tongue -> enhanced effective Bjerknes feedback
Summary & remarksSummary & remarks In MIROC5, a parameter for the cumulus entrainment () greatly affects the ENSO amplitude
ENSO controlling mechanisms involve: Direct changes in convective systems over the E.
Pacific Coupled feedback (incl. ENSO structural change)
The mean meridional precipitation contrast over the E. Pacific
is a relevant indicator of the ENSO amplitude in MIROC.
* the former is not necessarily the cause of the latter!!
Generality? Similar experiments with the other GCMs desired Implication for the future change of ENSO
CTDI-ENSO in CMIP3 modelsCTDI-ENSO in CMIP3 models
Axes of the parametric and structural uncertainties are quite different!!
CTL or 20C
GDFL CM2.1(by J-S Kug)
MIROC5
CMIP3
CTDI-ENSO in CMIP3 modelsCTDI-ENSO in CMIP3 models
Sensitivity to increasing CO2 agrees well with the axis of the parametric uncertainty in MIROC5 → by chance?
2xCO2 or A1b
What’s the issues for CMIP5/AR5?What’s the issues for CMIP5/AR5?
TODO
Theory & GCM (e.g. BJ index -> CMIP3/CMIP5 outputs)
Verification of convective processes using TRMM Combined analyses to AMIP+20C Single param. perturbed experiments -> PPE Climate sensitivity and ENSO changes Extensive use of near-term predictions (assimilation/hindcasts)
“KNOWN” & UNKNOWN
Relatively robust: mean change (weakening of trades / shoaling of thermocline / warming in the e. Pacific) Not robust: ENSO property changes (amplitude/preference etc)
What’s the issues for CMPI5/AR5?What’s the issues for CMPI5/AR5?
Result from the Hadley Centre PPE
Toniazzo et al. (2008)
?
Equilibrium climate sensitivity [K]
Nin
o 3
.4 S
ST s
td d
ev
[K]
Does this occur only when the model’s ENSO is controlled by low clouds? But, it seems consistent with MIROCs, too …
backup
2003 2007 2008 2009 2010 2013
AR4 AR5
MIROC3.2T42+1deg (med)T106+1/4x1/6deg (hi)
RR2002 “Kakushin”
AR5 data submission
MIROC historyMIROC history
Near-term
MIROC4.0(bug fixed version of 3.2)T42+1deg (med)T213+1/4x1/6deg (hi)
MIROC-ESMT42L80+1deg
MIROC4.1(prototype new model)
MIROC5.0T85+1deg (med)
Near-term
Long-term
Earth SimulatorEarth SimulatorEarth SimulatorEarth SimulatorEarth SimulatorEarth Simulator 22Earth SimulatorEarth Simulator 22
Guilyardi et al. (2009)
IntroductionIntroductionENSO diversity in CMIP3 models -> Controlling ENSO in complex system is still challenging
MIROC3 (for AR4) -> MIROC5 (for AR5)Most of the atm. physics schemes replaced
Std resolution: T85L40 atm. 0.5x1 deg ocean
ENSO was greatly improved
MIROC5
MIROC3med
Mechanism of the convective controlMechanism of the convective control
What is likely to be happening in MIROC5: Large (effective entrainment) → deep cumulus suppressed (→ more congestus in ITCZ → drying the cold tongue due to subsidence)→ strong north-south moisture contrast in the eastern Pacific (mean state change)→ precip./x response to El Nino confined to the western-central Pacific → weaker effective Bjerknes feedback→ weak ENSO
Feedback to the mean state
New version of New version of MIROCMIROCNew version of New version of MIROCMIROC MIROC3 (for AR4) MIROC5 (for AR5)
Atmos. Dynamical core Spectral+semi-Lagrangian (Lin & Rood 1996)
Spectral+semi-Lagrangian(Lin & Rood 1996)
V. Coordinate Sigma Eta (hybrid sigma-p)
Radiation 2-stream DOM 37ch (Nakajima et al. 1986)
2-stream DOM 111ch (Sekiguchi et al. 2008)
Cloud Diagnostic (LeTreut & Li 1991) + Simple water/ice partition
Prognostic PDF (Watanabe et al. 2009) + Ice microphysics (Wilson & Ballard 1999)
Turbulence M-Y Level 2.0 (Mellor & Yamada 1982)
MYNN Level 2.5 (Nakanishi & Niino 2004)
Convection Prognostic A-S + critical RH (Pan & Randall 1998, Emori et al. 2001)
Prognostic AS-type, but original scheme (Chikira & Sugiyama 2010)
Aerosols simplified SPRINTARS(Takemura et al. 2002)
SPRINTARS + prognostic CCN (Takemura et al. 2009)
Land/River
MATSIRO+fixed riv flow new MATSIRO+variable riv flow
Ocean COCO3.4 COCO4.5
Sea-ice Single-category EVP Multi-category EVP
New convection New convection schemeschemeNew convection New convection schemescheme
Chikira and Sugiyama (2010)
Entrainment rate (Conventional A-S scheme: prescribedC-S scheme: dependent upon buoyancy and cloud-base mass flux
Mixture of A-S and Gregory schemeA-SC-S
Deep cumulus
altit
ude
Strong w’ -> large
Shallow cumulus
Weak w’ -> small
Vertical profiles of in a single column model
Cloud type
eta
What’s the consequence?
Both work to increase middle level cumulus that was less in A-SNot necessary to use empirical cumulus triggering function
ENSO in MIROC5ENSO in MIROC5
A-O coupling strength
Guilyardiet al. (2009)
MIROC3med
MIROC5
Mean state differencesMean state differences
SST
Narrow warm pool, but the single ITCZ is well reproduced over the e. Pacific
Obs.
precipitation
model
Mean state differencesModel clim.
Qcum
L575-L500
More congestus?
Feedback coefficients
Both differences in and do not explain the different ENSO amplitude!
Comparison of the ENSO structure
Contour: regression of Eq. temperature anomaly on to Nino3 (per 1K)Shade: difference from the grand ensemble meanWhite contour: 19,20,21 degC mean isotherms
Mean state differencesRH in the eastern Pacific
Wet
Dry
Contour: annual mean clim.Shade: diff from the ensemble mean
RH-precipitation relationshipRH600 histgram Composite Pr. wrt RH600
Wet (dry) mid-troposphere is less (more) frequent in Nino3 region for larger
“Rich-get-richer” for larger
Mechanism of convective control Composite cumulus heating wrt CAPE in AGCM
Opposite direction of changein congestus clouds
Large (efficient entrainment)works to prevent deep cumulusconvection
QuestionSmall but cooler cold tongue (=larger zonal SST gradient) for large is it consistent with weaker ENSO?
A simple tropical climate model (Jin 1996, Watanabe 2008)
dw
0 ( )r eT T
*0
0
1 tanh ( ) /( )
2
ese r r r
H h z hT T T T
e wh h bL
( ) ( ) e see T e r
m
T TT T T w
H
2w wrbL
h rh
Stationary solutions
Question
Cooler cold tongue & weaker ENSO can coexist if -1 ∝ bL
Obs. Mean Te
Larger Larger
Rad
iativ
e he
atin
g
Bjerknes feedback efficiency
Std of J96
Range of mean Tein four runs
Can feedback factors explain the Can feedback factors explain the model’s diversity?model’s diversity?
r > 0, may be consistent with what means
Lloyd et al. (2009)
net heat flux damping)
(Bjerknes feedback)
Nin
o3 S
ST
Std
Dev
ENSO parameters in CMIP3 models
r < 0, inconsistent with what means
Convective control of ENSO?Convective control of ENSO?Most of the recent studies point out the role of cumulus parameterization in ENSO simulationsCCSM3 : Cumulus convection (Neale et al. 2008)
GFDL CM2: Cumulus convection (Wittenberg et al. 2006)IPSL: Cumulus convection (Guilyardi et al. 2009)SNU: Cumulus convection (Kim et al. 2008)HadCM3: Low cloud (Toniazzo et al. 2008)
What is meaningful with MIROC5? ー ENSO controlled by a single parameter (1D phase space) ー mean state changes are not large (but large for the TRH)
Generality ? ー diff model has diff bias, so the mechanisms may not be unique
Mean state (SST)Mean state (SST)
Mean state (precipitation)Mean state (precipitation)
seasonal cycles over the eastern Pacific
Watanabe et al. (2010)
CMAP Model EM Diff L575-L500
Mean state and ENSOMean state and ENSO
seasonal cycles of clim SST & ENSO amplitude
Nino3 SST mean seasonal cycle Nino3 SST std dev
Mean state differencesSST
SST is warmer in E. Pacific when ENSO is stronger, but the difference is quite small (less than 2 %)
Contour: annual mean clim.Shade: diff from the grand ensemble mean
Mean state differences
Wetter in E. Pacific for larger ENSOThe absolute difference is quite small (less than 1mm/dy), but relative differenceis quite large (more than 50%!)
Precipitation Contour: annual mean clim.Shade: diff from the grand ensemble mean
ENSO in MIROC5ENSO in MIROC5
SST mode or thermocline mode?
Guilyardiet al. (2006)
Convective control of ENSONew version of MIROC (MIROC4.5)
State-dependent entrainment in cumulus scheme (Chikira 2009)
2 ,
aB
w
Assumption between the entrainment rate and updraft velocity w (Gregory 2001)
2 2
2 (1 )w w
a Bz
The parameter is found to control the frequency ofdeep cumulus clouds (->large, suppress deep clouds)hence affect ENSO amplitude
Guilyardi et al. (2009)
=0.55
=0.5
=0.525
MIROC3.2
Convective control of ENSO
SST
T along Eq.
Pr/SLP/
Regression with Nino 3 index
Mean climate is quite similar to each other; nevertheless, ENSO amplitude is different with factor 2!!
=0.55 =0.5
Implication to 20Implication to 20thth century century trendtrendMIROC3 MIROC5
Cl trend(%/100y)
TropicalCl (30S-30N)
Decrease (-0.28%/100y) Increase (+0.47%/100y)
Likely due to fast response (but change is much slower) (CO2 increase; abrupt vs gradual) -> (fast response)?
20C runs
SST trend(K/100y)
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