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Les simulations CMIP5 « near term » au Cerfacs : choix stratégiques et état
d'avancement
Kickoff EPIDOM
CERFACS GIEC Team:
Christophe Cassou, Emilia Sanchez-Gomez, Elodie Fernandez, Marie Pierre Moine,
Laure Coquart, Yohan Ruprich-Robert, Laurent Terray
… et nos collègues du CNRM
Kickoff EPIDOM
Les expériences décennales
le setup expérimental
le modèle CNRM-CM5
Stratégies d’initialisation : nudging de l’océan vers la réanalyse
Expériences du nudging: impact de l’initialisation
Résultats préliminaires pour les premières prévisions
Plan de la présentation
Experimental design (historic and scenario runs)
Spin-up (300 yr)
SPIN UPControl (1000 yr)
External forcing1850
CONTROLHISTORIC (15 members)
Historic run (1850-2012)
External forcing1850-2012
Initial conditions from the CONTROL exp.
Experimental design for decadal experiment (novelty in CMIP5)
SCENARIO (2008-2100)
Observations
1960 200510 yr experiments
1965 1970 Every 5 years…….
1960 2005198030 yr experiments
3-10 members per ensemble
Evolutive external forcing
Initial conditions taken from « observed » values!!
1. Les expériences décennales
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1. Les expériences décennales: CMIP5
Summary of decadal experiments in CMIP5CORE: 3 membres
« BONUS »
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1. Les expériences décennales: CMIP5
Work in progress at CERFACS:
10 yrs decadal runs started at 1st January of 1960, 1965, 1970, …, 2005 (10) started at 1st January of 1960, 1965, 1970, …, 2005 (3, GHG, Vol. aero, cte) started at 1st January of 1961, 1966, 1971, …, 2006 (10) 30 yrs decadal runs
started at 1st January of 1960, 1980, 2005 (10) started at 1st January of 1961, 1981, 2005 (10)
Additional experiments 30yrs for 2005 initialized runs :
Prediction with 2010 Pinatubo (3) Prediction with 2010 solar minimum (3) GHGs, Vol. aero cte (3)
Full Initialisation : initial conditions from nudging experiments
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1. Les expériences décennales : l’outil
Land surface scheme SURFEX
AtmosphereARPEGE-Climat, 1.4° , L31
OceanNEMO v3.2 ORCA1 L42
24h
River routingTRIP
24h
24h
Sea IceGELATO
24hOASIS
CNRM-CM5 (Voldoire et al. In preparation)
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1. Les expériences décennales : l’outil
SST versus LEVITUS (CNRM-CM5)
SSS versus LEVITUS (CNRM-CM5)
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1. Les expériences décennales : l’outil
Variability Modes :
ENSO
5yr 3yr2.8 – 3.5 yr
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1. Les expériences décennales : l’outil
Variability Modes :
PNA
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1. Les expériences décennales : l’outil
Variability Modes :
NAO
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1. Les expériences décennales : l’outil
Meridional Overturning Circulation
MOC time series at 40°N
Comparison to RAPID_ARRAY measures
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1. Les expériences décennales : l’outil
Heat transport
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1. Les expériences décennales : l’outil
Sea Ice Extent (versus NOAA observations)
MAX MIN10e+9 m2 10e+9 m2
2. Stratégies d’initialisation
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Objective : To find ocean initial states compatibles at the same time with
the model climatology and also with the observational state nudging
2. Stratégies d’initialisation: nudging
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Nudging of NEMO (dkey tradmp, namtradmp)
No damping in the mixed layer(1/ β) =0
Sea surface restoring for T et S
Intermediate waters:β = 10 jours
Deep ocean (800m):β = 360 jours
depth)(1
... oTTt
T
)(1
... oSSt
S
To, So 3D observations
The parameter β varies with location
Equatorial band:(1/ β) =0
Near coastlines (300km):(1/ β) =0
Over the equator the timescale are very short and the nudging can alter the oceanic currents
2. Stratégies d’initialisation: nudging
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Sea surface restoring (namsbc_ssr)
Exemple: For a mixed layer of 50 m depth, this value corresponds to a relaxation of 2 months (2months are needed to Tk=1 = SSTobs)
)( 1 obskonsns SSTT
dT
dQQQ
Heat flux:
Heat flux at the surface
feedback term.SSTobs= observations
dT
dQ Feedback coefficient = -40W/m2/K
Fresh water flux:
1
13
1 )(
k
obsktso S
SSSSeEMPEMP
Fresh water budget at the surface
Feedback term.SSSobs= observations
Feedback parameter = -167 mm/days
2. Stratégies d’initialisation: nudging
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Nudging to the ECMWF ocean reanalysis NEMOVAR (ORCA1°) 1958 -2008
Several tests have been performed to set the optimal parameters for thenudging
HISTNUD1 free between (1°S – 1°N)HISTNUD15 free between (15°S – 15°N)
2. Stratégies d’initialisation: nudging
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Annual time series of heat content averaged over the entire basins. The impact of nudging differs from one basin to another.
J/m2
NEMOVAR1HISTNUD15
HISTNUD1
2. Stratégies d’initialisation: nudging
The Impact of nudging on the Heat transport
2. Stratégies d’initialisation: nudging
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Comparison to RAPID_ARRAY measures
3. L’impact de l’initialisation
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10 years experiments initialised on 1st January of 1960, 1965, …, 1990 from HISTNUD15 and HISTNUD1
GLOBAL SST
HISTNUD15
HISTNUD10.08°C on average
3. L’impact de l’initialisation
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Initial shock: First year run of 20deg isotherme between 2°S - 2°N
HISTNUD15
HISTNUD1
No nudging
NEMOVAR1
Decadal15
Decadal1
PACIFIC OCEAN
longitude
depth
3. L’impact de l’initialisation
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HISTNUD15
HISTNUD1
No nudging
NEMOVAR1
Temperature differences between 2°S, 2°N for the 1st January and isotherme at 20deg
degC
degC
degC
PACIFIC OCEAN
3. L’impact de l’initialisation
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PACIFIC OCEANZonal velocity differences between 2°S, 2°N for the 1st January Contours: NEMOVAR1
m/s
m/s m/s
3. L’impact de l’initialisation
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Initial shock: First year run of 20deg isotherme between 2°S - 2°N
HISTNUD15
HISTNUD1
No nudging
NEMOVAR1
Decadal15
Decadal1
ATLANTIC OCEAN
3. L’impact de l’initialisation
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HISTNUD15
HISTNUD1
No nudging
NEMOVAR1
Temperature differences between 2°S, 2°N for the 1st January and isotherme at 20deg
degC
degC
degC
ATLANTIC OCEAN
3. L’impact de l’initialisation
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ATLANTIC OCEAN Zonal velocity differences between 2°S, 2°N for the 1st January Contours: NEMOVAR1
m/s
m/s m/s
Résultats préliminaires pour les prévisions
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Unbiased forecasts, SST and heat content 300m
NEMOVARHISTNUD15
GLOBAL Heat Content GLOBAL SSTs
Atlantic Ocean SSTs
Historic runs
ACC SSTs
Résultats préliminaires pour les prévisions
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Anomalies of SSTs after removing the mean systematic bias
NEMOVAR1 HISTNUD15
GLOBAL SSTs ATLANTIC (35°S) SSTs
PACIFIC (35°S) SSTs INDIAN (35°S) SSTs
Résultats préliminaires pour les prévisions
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Heat content 300m (anomalies) after removing the mean systematic bias
NEMOVAR1 HISTNUD15
GLOBAL HC300 ATLANTIC (35°S) HC300
PACIFIC (35°S) HC300 AMO (35°S) HC300
Conclusions
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A nudging methodology to generate initial states has been presented. The nudging to T and S seems to alter somehow the ocean transports (heat and MOC) comparing to a non nudged simulation.
When initialising from nudging experiments, the model initial shock is enhanced as the nudging to ocean reanalyses is « stronger ».
The initial shock is identified as the generation of El Niño states due to the model heat release.
When initialised from HISTNUD15, the model reaches the historical run in aproximately 3-4 yrs.
The model drift has a regional behaviour, in particular there is a strong warming drift in the Southern Hemisphere (south out of 35°S)
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1. Les expériences décennales : l’outil
Zonal mean temperature and salinity bias, Atlantic Ocean
Differences CNRM-CM5 – LEVITUS climatology