CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 1

Joint Proposal to WGOMD for a community ocean model experiment

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 2

Background

• Seasonal Forecasts is an ideal test bed to asses the quality of the GCMS used in future climate projections:

Need ocean initial conditions to carry out experiments Not all the groups have ocean data assimilation systems in place.

• WGOMD is about to discuss experimental setup to asses ocean model performance in the representation of the inter-annual variability. Possibility of X-Panel interaction and feedback.

• The proposed experiment could answer some outstanding questions about the key elements needed to improve the representation of the Pacific basin and ENSO.

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 3

Questions from the Pacific Panel

• There are known model deficiencies in the representation of the Pacific climate:

Upwelling off the South American Coast Cold tongue penetrating too far west Too weak/too strong east-west slope of the thermocline Equatorial heat content (IT/meridional transport, vertical mixing) …

• Is it possible to say which are the dominant source of error?

Forcing fields? Model parameterizations/configuration? Model resolution? Parameterization of air-sea interaction?

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 4

Proposal

• Conduct a long ocean model simulation (20-40 years) with a variety of models, using inter-annually varying atmospheric reanalysis (ERA40-ENACT, NCEP-CORE, JMR-25…). This long integration can be used as:

a CNTL experiment to answer some of the above questions (see later)

To provide initial conditions for concerted seasonal forecast experiments.

• Conduct additional integrations with each model (optional), to test sensitivities:

Different forcing fields Different resolution Different parameterization, bulk formulae, ….

• Need to agree the specifications for the CNTL integration.

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 5

Sensitivities: Compute and Compare

•Sensitivity to Forcing fluxes:

•Sensitivity to Resolution:

•Sensitivity to Model:

•Sensitivity to Bulk Formula:

•Sensitivity to P-parameterization:

CteBPMRFXF

,,,

CteBPMFRXR

,,,

CteBPRFMXM

,,,

CteRPMFBXB

,,,

CteBRMFPXP

,,,

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 6

Sources of Uncertainty

EQPAC

0.00

0.05

0.10

0.15

0.20

spre

ad

EQATL

0.00

0.05

0.10

0.15

spre

ad

EQIND

0.00

0.05

0.10

0.15

0.20

spre

ad

NINO3

0.00

0.05

0.10

0.15

0.20

0.25

0.30

spre

ad

DTRATL

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

spre

ad

INDPL

0.0

0.1

0.2

0.3

spre

ad

All

ERA40

ERA40-No data

ERA40-Assim

12m-rm seasonal anom: EQPAC Averaged temperature over the top 300m

1950 1960 1970 1980 1990 2000Time

-1.0

-0.5

0.0

0.5

1.0

1.5

allsdv_ensm= 0.269spread= 0.239s/n_ensm = 1.127

era40sdv_ensm= 0.278spread= 0.145s/n_ensm = 1.912

era40-ctrlsdv_ensm= 0.338spread= 0.117s/n_ensm = 2.887

era40-assmsdv_ensm= 0.332spread= 0.085s/n_ensm = 3.910

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 8

Assimilation and Uncertainty T300

Long period 1956-2005:

Large part of uncertainty comes

from forcing fluxes

1956-2005

EQPAC

0.00

0.05

0.10

0.15

0.20

spre

ad

EQATL

0.00

0.05

0.10

0.15

spre

ad

EQIND

0.00

0.05

0.10

0.15

0.20

spre

ad

TRPAC

0.00

0.02

0.04

0.06

0.08

0.10

0.12

spre

ad

TRATL

0.00

0.02

0.04

0.06

0.08

0.10

0.12

spre

ad

NPAC

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

spre

ad

NATL

0.00

0.02

0.04

0.06

0.08

0.10

spre

ad

GLOBAL

0.00

0.01

0.02

0.03

0.04

0.05

0.06

spre

ad

EQPAC EQATL EQIND TRPAC

TRATL NPAC NATL GLOBAL

ALL

SAME FORCING (ERA40)

OCEAN MODEL

ASSIMILATION SCHEME

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 10

-1.5 -1.2 -0.9 -0.6 -0.3 0temperature

-400

-200

Dep

th (m

)

S3-a S3-cMean(199301-200201) of Model minus Observations

eq3-All in situ data

50OE 100OE 150OE 160OW 110OW 60OW 10OW

Longitude

500

400

300

200

100

0

Depth

(m

etr

es)

500

400

300

200

100

0Plot resolution is 1.4063 in x and 10 in yZonal section at 0.00 deg NICODE=178 contoured every 0.0002 XXXHOPE gcm:: 0001

Interpolated in y 0 ( 31 day mean)

difference from20020101 ( 31 day mean)

-0.0008

-0.0006-0.0

00

4

0.0002

0.0012

-0.0024

-0.002

-0.0016

-0.0012

-0.0008

-0.0004

0.0002

0.0006

0.001

0.0014

0.0018

0.0022

MAGICS 6.9.1 hyrokkin - neh Tue Jul 25 19:19:38 2006

Mean Assimation Temperature Increment

-0.4 -0.2 0 0.2 0.4 0.6temperature

-400

-200

Dep

th (m

)

S3-a S3-cMean(199301-200201) of Model minus Observations

eqind-All in situ data

Western Pacific Equatorial Indian

Analysis minus Observations

DATA ASSIM

NO DATA ASSIM

• Equatorial Pacific heat content is model dependent

• Slope of Pacific Eq. thermocline controlled by winds

ERA40 produces weak thermocline slope in most models

• Too diffuse thermocline in Indian Ocean?

Sensitivities: preliminary results from ENACT/GSOP

MEAN STATE:

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 11

Strawman for the CNTL integration

• From spin up, launch the integrations, using daily atmospheric forcing fluxes plus some restoring terms:

3D relaxation to climatology of T and S (~10 year time scale) Strong relaxation to time-varying values of SST (~2-3 days t.s) Relaxation to climatological Surface Salinity (1 year t.s) If free surface, volume preserving constrains.

• The restoring terms are used to diagnose errors.

• Atmospheric forcing (daily values): Momentum flux: ERA40 0-24 wind stress Heat flux:

o ERA40 0-24 solar, latent and sensible heat fluxes. PLUSo Strong relaxation to daily values of SST (~2 days time scale) (Reynolds from

1982) Fresh Water flux:

o ERA40 0-24 PME + ENACT correctiono Weak Relaxation to climatological SSS (~12 month time scale)o If free surface, some volume preserving constrains.

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 12

CNTL integration at ECWMF

• Decent Inter-annual ENSO variability

50O E 100OE 150OE 160OW 110OW 60OW 10OW

Longitude

40OS

30OS

20OS

10O

S

0O

10O

N

20O

N

30O

N

40ON

Latit

ude

40OS

30OS

20OS

10O

S

0O

10O

N

20O

N

30O

N

40ON

Plot resolution is 1 in x and 1 in ySurface fieldSea level contoured every 0.1 mCorrel: Control

Interpolated in y

20020101 ( 9 year mean)

0.5 0.5

0.5

0.5

0.5

0.6

0.6

0.6

0.6

0.6

0.6

0.7

0.7

0.7

0.7

0.7

0.7

0.8

0.8

0.8

0.80.9

0.9

-6

-5

-4

-3

-2

-10.5

0.6

0.7

0.8

0.9

0.98

MAGICS 6.9 hyrokkin - neh Thu Sep 9 12:12:36 2004

Correlation with altimeter data (1993-2003)

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 13

CNTL integration at ECWMF

• Some MOC variability

1960 1970 1980 1990 20001.0·107

1.5·107

2.0·107

2.5·107

3.0·107

0001 ATL26N 168 vmona_d.assim_an0 Trend= -0.074 +/- 0.020 Sv/y; In 10y = -4.1%0001 ATL26N 168 vmona_d.control_an0 Trend= -0.029 +/- 0.013 Sv/y; In 10y = -2.0%euj7 ATL26N 168 vmona_d.control_an0 Trend= -0.009 +/- 0.006 Sv/y; In 10y = -0.6%Brydend estimation Trend= -0.159 +/- 0.162 Sv/y; In 10y = -8.7%

CLIVAR WORKSHOP. Barcelona 4-6 June 2007: Joint Proposal to WGOMD 14

CNTL integration at ECWMF

• As initial conditions, decent forecast skill.

0 1 2 3 4 5 6 7Forecast time (months)

0.4

0.5

0.6

0.7

0.8

0.9

1

An

om

aly

co

rre

latio

n

wrt NCEP adjusted OIv2 1971-2000 climatology

NINO4 SST anomaly correlation

0 1 2 3 4 5 6 7Forecast time (months)

0

0.2

0.4

0.6

0.8

Rm

s e

rro

r (d

eg

C)

Ensemble sizes are 3 (esj6) and 3 (esj6) 76 start dates from 19870101 to 20051001

NINO4 SST rms errors

Fc esj6/m1 Fc esj6/m0 Persistence Ensemble sd

MAGICS 6.10 hyrokkin - neh Thu Sep 7 19:11:46 2006

S3 Nodata S3 Assim