les simulations cmip5 « near term » au cerfacs : choix stratégiques et état d'avancement...

Les simulations CMIP5 « near term » au Cerfacs : choix stratégiques et état

d'avancement

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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

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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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SST versus LEVITUS (CNRM-CM5)

SSS versus LEVITUS (CNRM-CM5)

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Variability Modes :

ENSO

5yr 3yr2.8 – 3.5 yr

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Variability Modes :

PNA

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Variability Modes :

NAO

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Meridional Overturning Circulation

MOC time series at 40°N

Comparison to RAPID_ARRAY measures

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Heat transport

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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


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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


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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)


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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


The Impact of nudging on the Heat transport


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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


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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


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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


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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


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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


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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


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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


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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


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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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Zonal mean temperature and salinity bias, Atlantic Ocean

Differences CNRM-CM5 – LEVITUS climatology

les simulations cmip5 « near term » au cerfacs : choix stratégiques et état d'avancement...

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