Simulated Air-Sea CO2 Fluxes in the Pacific: Multidimensional Statistical

Analysis of Model Performance

J. C. Orr 1, K. G. Caldeira 2, K.E. Taylor 3,and the OCMIP Group*

1LSCE/CEA/CNRS and IPSL (France)2LLNL Carbon and Climate Group3PCMDI/LLNL

http://www.ipsl.jussieu.fr/OCMIP

AGU Ocean Sciences MeetingPresentation OS32I-09

Wed 13 Feb 2002

OCMIP Group

• AWI (Bremerhaven, Germany): R. Schlitzer, M.-F. Weirig • CSIRO (Hobart, Australia): R. Matear• IGCR/CCSR (Tokyo, Japan): Y. Yamanaka, A. Ishida• IPSL (LSCE, LODyC, Paris, France): J. Orr, P. Monfray, O. Aumont, J.-Cl.Dutay,

P. Brockmann • LLNL (Livermore, CA, USA): K. Caldeira, M. Wickett• MIT (Boston, USA): M. Follows, J. Marshall• MPIM (Max Planck Institut fuer Meteorologie—Hamburg, Germany): E. Maier-Reimer • NCAR (Boulder, USA): S. Doney, K. Lindsay, M. Hecht • NERSC (Bergen, Norway): H. Drange, Y. Gao• PIUB (Bern, Switzerland): F. Joos, K. Plattner • PRINCEton (Princeton, USA): J. Sarmiento, A. Gnanadesikan, R. Slater, R. Key• SOC (Southampton Oceanography Centre/Hadley Center, UK): I. Totterdell, A. Yool • UL (University of Liege/University Catholique de Louvain, Belgium):

A. Mouchet, E. Deleersnyder, J.-M. Campin• PMEL/NOAA (Seattle, USA): J. Bullister, C. Sabine• PSU (Penn. State, USA): R. Najjar, F. Louanchi• UCLA (Los Angeles, USA): N. Gruber, X. Jin

OCMIP-2 Model Simulations

• Tracers– CFC-11 and CFC-12

– C-14 (Natural and Bomb Components)

– He-3

• Carbon– Past (Preindustrial: No Biology, Common Biology)

– Historical (Followed observed atmospheric CO2)

– Future (IPCC IS92a and S650 until 2300)

– Sequestration (7 sites, 3 depths, 2 scenarios)

Sea-Air CO2 Flux in 1995: Data vs. Model mean, σ, Range (mol m-2 yr-1)

Taylor Diagram: Global, Seasonal, Sea-Air CO2 Flux Map

Pacific Regional Sea-Air CO2 Fluxes:

Space-Time ComparisonNorth Pacific: 22oN-70oN Equatorial Pacific: 22oS-22oN

Pacific Sea-Air CO2 Flux in 1995 (Zonal Integral, Annual Mean, Pg C yr-1 deg-1)

North PacificAnnual Mean Sea-Air CO2 Flux in 1995 (mol m-2 yr-1)

Eq. PacificAnnual Mean Sea-Air CO2 Flux in 1995 (mol m-2 yr-1)

Pacific Seasonal Anomaly of Zonal Mean Sea-Air CO2 Flux in 1995

(mol m-2 yr-1)

Conclusions: Pacific Sea-Air CO2 Fluxes

• Models vs. data estimates of sea-air CO2 fluxes in the Pacific:– Poor agreement

• Spatial anomaly (longitudinal variability) • Seasonal anomaly map (seasonal variability)

– Better agreement (N. Pacific, Tropical Pacific)• Zonal mean (latitudinal variability)

• Data-based estimates (Takahashi et al.):– North Pacific: largest variability; seasonality dominates – Tropical Pacific: latitudinal, longitudinal, seasonal variability

contribute equally – South Pacific: minor latitudinal variability (models exhibit

substantially larger contribution, which is unusual) • Taylor Diagram*: merits further use in model-data comparison and

model development

*Taylor, K. E., J. Geophys. Res., 106, D7, 7183-7192, 2001

South PacificAnnual Mean Sea-Air CO2 Flux in 1995 (mol m-2 yr-1)

PacificSeasonal Zonal Integral Sea-Air CO2 Flux in 1995 (Pg C yr-1 deg-1)

Pacific SeasonalZonal Mean Sea-Air CO2

Flux in 1995 (mol m-2 yr-1)

Air-Sea CO2 Flux by Component:Zonal Integral(Pg C yr-1 deg-1)

Conclusions: Taylor Diagram

• Taylor* Diagram: graphical evaluation of 5 global summary statistics (σdata, σmodel, r, R.M.S., Bias)

– rapid, intuitive first look useful in evaluating ocean as well as atmospheric models

*Taylor, K. E., J. Geophys. Res., 106, D7, 7183-7192, 2001

Basis for Taylor Diagram*

• Standard deviations (ref., model)• Correlation Coefficient R:

• Centered Pattern RMS error:

• Overall Bias:Law of Cosines:

*Taylor, K.E., J. Geophys. Res., 106, D7, 7183-7192, 2001

Key relationship:

Some Objective Summary Statistics

• Standard deviation (ref., model)• Correlation Coefficient R:

• Centered Pattern RMS error:

• Overall Bias:

OCMIP: Objectives

• Accelerate Model Improvement

Provide Infrastructure for International Collaboration– Forum

– Benchmarks

– Model Output Archive

– Analysis Tools

• Provide Constraints – Ocean Carbon Uptake (Loss)

– Global Carbon Cycle

Model Differences