Jim Hurrell OceanObs09 21-25 September 2009 OceanObs09: Ocean Information for Society Day III: Delivering Services to Society Session B: Forecasting Decadal-to-Centennial

Jim Hurrell OceanObs09 21-25 September 2009

OceanObs09: Ocean Information for SocietyDay III: Delivering Services to Society

Session B: Forecasting

Decadal-to-Centennial Prediction:Opportunities and Challenges

Jim Hurrell

Climate and Global Dynamics Division, NCAR

[email protected]


Seasonal to Interannual Prediction

Decadal prediction

Centennial prediction

Initial value problem

Boundary value problem

Boundary value

Climate Prediction

+ Initial value




CWP on Decadal Climate Variability, Predictability and Prediction

Contributing Authors

G. DanabasogluT. DelworthD. DommengetH. DrangeK. DrinkwaterS. GriffiesW. HazelegerN. Holbrook

B. KirtmanN. KeenlysideM. LatifJ. MarotzkeJ. MurphyG. MeehlT. PalmerH. Pohlman

T. RosatiR. SeagerD. SmithR. SuttonA. TimmermanK. TrenberthJ. TribbiaM. Visbeck




CWP on Decadal Climate Variability, Predictability and Prediction

Contributing Authors

G. DanabasogluT. DelworthD. DommengetH. DrangeK. DrinkwaterS. GriffiesW. HazelegerN. Holbrook

B. KirtmanN. KeenlysideM. LatifJ. MarotzkeJ. MurphyG. MeehlT. PalmerH. Pohlman

T. RosatiR. SeagerD. SmithR. SuttonA. TimmermanK. TrenberthJ. TribbiaM. Visbeck


Linear trend of surface temperatures1901 – 2005 ( C Century-1)

Mixture of internal variability and forced climate change

IPCC (2007)

°


Change in Winter Sea Level Pressure (1980-2008)(hPa)Dec-Mar

Pressure Falls

Pressure Rises

Decadal Climate Variability

1900-2009

1900-2009


Sahel Rainfall

Decadal Climate Variability

Interhemispheric SST Contrast

NH Cold

NH Warm

Strong relationship to SST changes


Warm North Atlantic linked to …

More rain

Less rain

North Atlantic SST

Ting et al. (2008)

Forced component

Internal variabilityCourtesy T. Delworth

DroughtDrought

Hurricanes


Open Questions and Challenges

• To what extent is decadal variability predictable? Higher Extratropical SST Predictability

IPCC AR4 Models (8900 yrs Control) 10 yr means

Potential Predictability in Surface Temperature

Boer and Lambert (2008)

potential predictability variance fraction (σv2/σ2)



• To what extent is decadal variability predictable?

Courtesy Tom Delworth in Hurrell et al. (2009)

Phenomena: Idealized Predictability Experiments

Perturbedensemble membersevolvecoherentlyfor twodecades


Projected Atlantic SST Change

Forced by External Processes

o “Committed” o Future Δradiative forcing

External Forcing


• To what extent is decadal variability predictable?• What are the mechanisms for decadal variability?

Interactions of Forced and Natural Variability

Latif et al. (2009)

Internal Processes

o Low-pass filtering of noiseo Slow internal variationso Coupled

Internal Processes


• Does oceanic variability have atmospheric relevance?


Pohlmann et al. 2006

+ AMOC- AMOC


Global Number of Temperature Observations (1980-2006)

Courtesy Tony Rosatiin Hurrell et al. (2009)

• Do we have the proper tools to realize the predictability?


Adequate climate observing system?

Argo

A major challenge for climate analysis and prediction: uneven observational coverage in both space and time; deep ocean and ice covered regions are poorly observed.


• Do we have the proper tools to realize the predictability?

Adequate climate observing system? Reliable assimilation systems to initialize models?


Internal Variability

Scenario

Model

Internal

Scenario

Model

Decadal Mean Surface TGlobal Regional

Sources ofuncertainty

Hawkins and Sutton 2009

Are models “good enough” to make skillful predictions?

Rienecker et al.Balmaseda et al.


First Attempts at Decadal PredictionCorrelation skill in predicting 10-yr mean SAT anomalies

(Hashing indicates skill over radiative forcing only)

Keenlyside et al. 2008Keenlyside et al. 2008

10-yr, 3-member hindcasts Every 5 years from 1955-2005

ECHAM5/MPI-OM

Initial Conditions: coupled model SSTs restored to observed anomalies


First Attempts at Decadal Prediction

Observations

Observations

Global Surface Temperature

• Initialization strategies and other aspects differ considerably

• All include estimates of changes in external forcing

• Large differences in future predictions


Decadal Prediction Protocol(CMIP5)

• 10 year integrations with initial dates from 1960-2005• Ensemble predictions (minimum 3 members)• Ocean initial conditions should be in some way representative of the observed anomalies or full fields for the start date• Land, sea-ice and atmosphere initial conditions left to the discretion of individual modeling groups• 1960, 1980, and 2005 integrations extended 30 years

WCRP/IGBP Aspen Workshop(July 2006)


Concluding Thoughts

• Decadal prediction will require:

– Better characterization and mechanistic understanding (determines level of predictability)

– Advanced assimilation and initialization systems– Advanced models (resolution, physics)– Estimates of future changes in radiative forcing– Sustained global observations

• Decadal climate variability:

– Mixture of internal variability and forced climate change

– Significant societal relevance: will be part of IPCC AR5

– Time to explore is now, but:

• Increased dialog with sector communities to– make best use of predictions, better define

requirements and drive improvement in predictive systems


• Ocean observations are critical for decadal prediction:• For model improvement and verification• For initialization and characterization of decadal

variability

Ocean Observations

• Must continually assess utility of existing and planned ocean observations for decadal prediction systems

• Sustain existing observing system components: e.g.,• Argo, altimetry, SST, sea ice• Moorings (tropical, boundary current, OceanSITES)• Address under-sampling • Full water column observations (initialize MOC)• Utility of Argo-type measurements below 2000 m• Need for denser observing system in “critical

regions” to assess observational requirements for decadal information


Thank You

Happy Birthday Lisa!

Documents

Jim Hurrell OceanObs09 21-25 September 2009 OceanObs09: Ocean Information for Society Day III: Delivering Services to Society Session B: Forecasting Decadal-to-Centennial