Hindcast Skill in the new coupled NCEP Ocean-Atmosphere Model

Suranjana Saha, Wanqiu Wang, Hua-Lu Pan

and the NCEP/EMC Climate and Weather Modeling Branch

Environmental Modeling Center, NCEP/NWS/NOAASpecial Acknowledgements : Sudhir Nadiga, Jiande Wang, Qin Zhang, Shrinivas Moorthi, Huug van den Dool

E

M

C

Introduction

A new global coupled atmosphere-ocean model has recently been developed at NCEP/EMC.

Componentsa) the T62/64-layer version of the current NCEP atmospheric GFS (Global Forecast System) model and

b) the 40-level GFDL Modular Ocean Model (version 3)

Note:Direct coupling with no flux correction

This model will replace the current operational NCEP coupled model (CMP14) for SST prediction in 2004.

Hindcast Skill Assessment

• 5-member ensemble over 22 years from 1981-2002

• January and April initial conditions• Other months to follow

• 9 month runs

• Initial atmospheric states 0000 GMT 19, 20, 21, 22, and 23 for each month• Reanalysis-2 archive

.• Initial ocean states NCEP GODAS (Global Ocean Data

Assimilation System) 0000 GMT 21st of each month • Same for all runs• GODAS operational September 2003

Hindcast Skill Assessment (cont)

• So far 220 runs have been made

• Hindcast skill • Estimated after doing a bias correction for each year• Uses model climatology based on the other years

• Anomaly correlation skill score for Nino 3.4 region SST prediction

• Skill maps • Global SST • U.S. temperature and precipitation.

• Comparisons with CMP14 and CASST

CoupledRed: monthly bias

Observed

Composite Warm and Cold Events

• Events exceed ERSST variance by

• 1.0 SD (warm)

• 0.75 SD (cold)

• Heavy black line is mean

+36 moPeak- 36 mo

Red: coupled model

SST Climatology on Equator

Ensemble Mean

CMP14CASST

April IC

January IC

CASST

CMP14

Ensemble Mean

RMS ErrorApril

RMS ErrorJanuary

6 Month Lead (November)

from April IC

SST anomaly for 1981-2002

Note Amplitudes

Observed

Observed

6 Month Lead (August)

from January IC

SST anomaly for 1981-2002

Note Amplitudes

HindcastSeasonally (3 month) Averaged

SST Anomaly CorrelationApril IC

Note: large & persistent skill in tropics

HindcastMonthly Averaged

SST Anomaly CorrelationApril IC

June-September

Left: New Coupled SystemRight: CMP14

HindcastMonthly Averaged

SST Anomaly CorrelationApril IC

October-January

Left: New Coupled SystemRight: CMP14

HindcastSeasonally (3 month) Averaged

SST Anomaly CorrelationJanuary IC

Note: large & persistent skill in tropics

HindcastSeasonally Averaged

SST Anomaly CorrelationJanuary IC

Left: New Coupled SystemRight: CMP14

Hindcast3 month Averaged

U. S. Surface Temperature Anomaly Correlation

April IC

Note: areas of persistent skill > 60% at up to 6 month lead

U. S. Surface TemperatureHindcast Skill

3 Month AveragesApril IC

Comparison with CPCCCA Method

Note: Coupled System skillcomplementary to CCA

U. S. Surface TemperatureHindcast Skill

3 Month AveragesJanuary IC

Comparison with CPCCCA Method

Note: Coupled System skillcomplementary to CCA

Hindcast3 month AveragedU. S. Precipitation

Anomaly CorrelationApril IC

Note: areas of persistent skill > 60% at up to 6 month lead

U. S. PrecipitationHindcast Skill

3 Month AveragesApril IC

Comparison with CPCCCA Method

Note: Coupled System skillcomplementary to CCA

U. S. PrecipitationHindcast Skill

3 Month AveragesJanuary IC

Comparison with CPCCCA Method

Note: Coupled System skillcomplementary to CCA

MJO Forecasts (W. Wang)

Experiments damp: GFS03 with damped SST anomalies clim: GFS03 with climatological SSTs amip: GFS03 with observed SSTs coup: CFS03 with MOM3 ocean analysis

All forecasts to 45 daysComposite results

Phase 1

Phase 2

Phase 4

Phase 3

(Initiation)

(Max pos. ampl. Over IO)

(Max pos. ampl.Over WPAC)

(Decay)

Note: coupling necessary for propagation in Phases 1-3

Days 1-30

Coupled

AMIP

Climo

Damped

Observed

SST Expt.

Summary and Conclusions• CFS03 hindcast skill for January and April initial

conditions (1981-2002 ) have been evaluated

• For April, the SST AC skill over Nino 3.4 is better than CMP14 and CASST at all leads

• For January, the SST AC skill over Nino-3.4 is better than CMP14 and CASST for all leads, except lead 2

• Ensemble mean forecasts for U.S. temperature and precipitation show comparable skill to CPC’s CCA method.

• This skill is complementary to CCA as it manifests itself in different geographical areas and can be used in CPC’s operational seasonal consolidated forecast.

• Hindcasts for the rest of the calendar months are being performed

• Implementation is being planned for late 2004

Summary and Conclusions (cont)

New Climate Positions at NCEP/EMC

• UCAR Visiting Scientist Position at NCEP/EMC – Work with NCEP Coupled Model– http://www.earthworks-jobs.com/climate/ucar3101.htm

l• NCEP Climate Team Leader (GS-15)

– Coordinate development activities with community– Provide strategic guidance on NCEP’s Climate

Numerical Modeling activities– Participate actively in development activities with

EMC staff