1. GSOP Report Detlef Stammer Universität Hamburg  CLIVAR/GODAE Synthesis Evaluation Effort  CLIVAR Reference Data Management Issues

2. CLIVAR’s (WOAP’S) Synthesis Needs CLIVAR’s (WOAP’S) Synthesis Needs

3. Challenges  The spectrum of applications of ocean reanalyses for climate variability and prediction purposes spans over seasonal-to-interannual, decadal-to-centennial, and even millennial time scales.  These applications pose a range of accuracy and robustness requirements on ocean reanalyses.  Consequently, they necessitate somewhat different data assimilation approaches and evaluation.

4. Ocean Synthesis  Several global ocean data assimilation products are available today that in principle can be used for climate applications.  Underlying assimilation schemes range from simple and computationally efficient (e.g., optimal interpolation) to sophisticated and computationally intensive (e.g., adjoint and Kalman filter-smoother).  Intrinsically those efforts can be summarized as having three different goals, namely –climate-quality hintcasts, –high-resolution nowcasts, and –the best initialization of forecast models.

5. Synthesis Evaluation Synthesis Evaluation  Is needed to determine the quality of existing global ocean analysis/synthesis products and to assess their usefulness for climate research.  Will focus on global results and their usefulness for climate research purposes, oriented along GSOP science questions.  Needs to be done in a close collaboration with CLIVAR's basin panels to serve their implementation, e.g., ongoing and planned regional process experiments.

6. Quantities  The intercomparison study is oriented along global scientific questions:  1) THE OCEANS IN THE PLANETARY HEAT BALANCE: (1) heat storage, (2) heat transports and (3) ocean/atmosphere feedbacks.  2) THE GLOBAL HYDROLOGICAL CYCLE: (1) water balance, (2) rainfall variability and (3) salinity and convection.  3) SEA LEVEL: (1) sea level rise and (2) sea level variability.

7. GSOP/GODAE Synthesis Evaluation Workshop, Aug.31,Sept. 1, 2006 at ECMWF. The overall goals of the inter-comparison of global synthesis efforts are to:  Evaluate the quality and skill of available global synthesis products and determine their usefulness for CLIVAR.  Identify the common strength and weakness of these systems and the differences among them, as well as to identify what application can be best served by what synthesis approach.  Define and test climate-relevant indices that in the future should be provided routinely by ongoing or planned synthesis efforts in support CLIVAR and of the wider community.

8. Synthesis Evaluation  Individual synthesis efforts were ask to compute indices from their results prior to the workshop and make them available to the project for further evaluation.  Input has been solicited from individual basin panels regarding metrics and indices for global reanalyses and the identification of CLIVAR reference data sets.  The evaluation effort will be based on results available from the period 1950 to present, including those that cover the TOPEX/JASON-1 era.

9. Metrics  Systematic model-data comparison: RMS model data differences rel. to prior data errors.  Differences first guess/constrained model.  Comparison to reference data sets, e.g., surface fluxes.  Comparison with time series stations.  Computation of integral quantities.  Budgets, e.g., heat content and its change.  Model-Model differences (incl. first guess).

10. Agenda (1)  THURSDAY, AUGUST, 31:  8:30Goal of Synthesis Evaluation Effort and Charge to the meeting (D. Stammer)  8:45CLIVAR Data Sets (David Legler)  9:15CLIVAR Surface Flux Reference Data (Simon Josey)  9:45Discussion of Data and Error Requirements (Carl Wunsch)  SUMMARY of individual Synthesis Projects (10 min. each + hand outs)  14:10Ocean Indices from Data (OOPC, Albert Fischer)  14:30CLIVAR/GODAE Metrics for Ocean Analysis (Detlef Stammer)  14:50Data archiving/DODS (Peter Hacker and Paco Doblas-Reyes) (10 min. each)  15:30Group: RMS Model-Data misfits (P. Heimbach, D. Menemenlis)  16:30Group: Meridional Transports (A. Köhl)  17:30General Discussion  18:00Adjourn 

11. Agenda (2) FRIDAY, SEPTEMBER, 1  8:30Group: Surface Fluxes (L. Yu)  9:30Group: Sea Level Changes (Magdalena Alonso-Balmaseda)  10:00 Group: Heat and Salt Content (Anthony Weaver)  11:00Group: Transports through key regions (T. Lee)  13:00Group: Water Masses (K. Haines and T. Lee)  14:00Group: Indices (A. Fischer)  15:30Carbon Program and Synthesis (D. Wallace)  15:50 General Discussion  16:30Summary and Next Steps  17:00END OF MEETING

12. Outcome  Quantitative statement of the skill of available global synthesis products and their usefulness for CLIVAR.  Identification of common strength and weakness of systems and the differences among them.  Definition of climate-indices and diagnostic quantities to be produced on a regular basis.  Prototype synthesis support of global and regional CLIVAR research (will be extended as work progresses).  Basis for recommendations with regard to future synthesis resource planning.  GSOP Web site to present climate indices from ocean syntheses over last 50 years.  Counter part to OOPC indices from data alone.  Stimulation for WGOMD and IPCC to join in.

13. Intercomparison Quantities: 1. RMS Model-Data Misfits: (Discussion Leads: Patrick Heimbach and Dimitris Menemenlis)  Difference from WOA01 climatological (monthly, Jan.-Dec.) potential T & S  RMS misfit from Reynolds SST  RMS misfit from in-situ T & S profiles (including XBT, CTD, Argo, moorings)  RMS misfit from altimeter-derived SSH  RMS misfit from tide-gauge SSH 2. Meridional Transports: (Discussion Lead: Armin Koehl)  Timeseries of the period 1950-present of meridional overturning transport stream function of the global ocean, Atlantic (north of 34S), and Indo-Pacific (north of 34S) as a function of latitude and depth and for the global ocean as a function of latitude and potential density.  Timeseries of the period 1950-present of meridional heat and freshwater transports of the global ocean, Atlantic (north of 34S), and Indo-Pacific (north of 34S) as a function of latitude and Time series of maximum MOC strength and heat transport at 25N, 48N in North Atlantic

14. Intercomparison Quantities: 3. Heat and Salt Content (Discussion Leads: Magdalena Alonso Balmaseda; Anthony Weaver)  Monthly means of averaged temperature (proxy to heat content) and salinty over the upper 300m/750m and 3000m.  Time series for spatial averages within a list of 30 pre-defined boxes in various parts of the ocean. 4. Sea Level Changes (Discussion Leads: Anthony Weaver and Magdalena Alonso Balmaseda)  Monthly means of sea level, and optionally steric height and/or bottom pressure.  Time series for spatial averages within a list of 30 pre-defined boxes in various parts of the ocean. 5. Transports through Key Regions: (Dsicussion Lead: Tong Lee)  Indonesian throughflow volume transport  ACC volume transport through the Drake passage.  Florida Strait volume transport, temperature flux, and salinity flux.

15. Intercomparison Quantities:  6. Water Masses: (Discussion Lead: Keith Haines and Tong Lee)  18-C water volume in the N Atlantic Ocean, volumne-weighted average salinity of the 18C water as a function of month.  Annual Maximum mixed layer depth within the Labrador sea and the T,S properties of that mixed layer.  Warm-water volume in the equatorial Pacific (5S-5N, 120E-80W) AND tropical Pacific (20S-20N, 120E-80W),  Depth of 20 degree isotherm in Pacific Ocean as a function of longitude, latitude, and month. 7. Indices: (Discussion Lead: Albert Fischer)  Sea surface temperature anomaly indices averaged over lat-lon boxes in the ocean. Here are the indices: –Pacific: Nino1+2; Nino3; Nino3.4; Nino4 –Indian: SETIO; WTIO –N. Atlantic: Curry and McCartney transport index. 8. Surface Fluxes: (Discussion Lead: Lisan Yu)  Monthly means of net surface heat and freshwater flux as function of geographic location.  Time mean of net surface heat flux and freshwater flux over entire model domain.  Zonal averages of annual mean net surface heat flux and freshwater flux over the model domain.

16. Participating Groups ECCO (Estimation of the Circulation and Climate of the Ocean) (US) GECCO SODA (Simple Ocean Data Assimilation) POP (US) GFDL/NOAA (US) NCEP/NOAA (US) HYCOM (US)GMAO/GSFC (US) ECMWFINGV/ENACTCERFACS-LODYC/ENACT UK Met Office? MERCATOR/MERSEA?MOVE-GK-7BlueLink WGOMD and/or IPCC

17. ENSEBLESMOC

18. Bryden et al. (2006) Strength of the MOC: shown ins the change in MOC strengths at 25 degree N from 50 yr optimization, from 11 yr optimization and from Bryden et al., 2005

19. ECCO-SIO ECCO-SIO/50y + Ref. Bryden et al. (2005)

21. K-7 Max. MOC 25 o N Bryden et al. (2005) ECMWF

22. ENSEBLES Heat/FW transport Global Mean 25N (PW) Global Mean 20S (PW) Ind.- Pac. Mean 25N (PW) Atl. Mean 25N (PW) Atl. STD 25N (PW) Atl. Season al 25N (PW) Atl. Drift 25N (PW/10 yr) Global Mean FW 30S (Sv) Global Mean FW 25N (Sv) Model Details Method Details Ganachaud & Wunsch (2000) 1.80-0.800.501.30 Macdonald (1998) 0.72-0.3 AWI LSG 3.5 o,Lev adjoint DEPRESYS ECCO-JPL1.45-1.300.441.010.30-0.370.50-0.35 MIT 1-1/3 o, Lev KPP, GM partitio n Kalma n ECCO-SIO1.40-0.440.450.960.210.13-0.080.35-0.31 MIT 1 o, Lev, KPP, GM adjoint ECCO-50yr1.26-0.630.380.880.210.14 0.034 0.0340.33-0.31 MIT 1 o,Lev, KPP, GM adjoint ECCO- GODAE 1.15-0.780.330.820.210.130.0330.55-0.31 MIT 1 o,Lev adjoint ECCO2- CS510 MIT CS,Lev ECMWF HOPE 1 o,Lev OI GFDL1.010.220.200.770.310.11-0.018MOM INGV2.2-1.10.71.450.250.11-0.270.82-0.45 OPA 2- 1/2 o,Lev, TKE, eddy vel multiva r. OI K-7 MOM3, 1 o Lev, KPP,GM adjoint MOVE MERCATO R OPA,Lev, TKE SOFA- OI SODA0.990.16-0.08 MOM 1-1/3 o Lev KPP,GM OI

23. K-7 Global Heattransport Ganachaud&Wunsch(1996)

24. K-7 Heat transport 25 o N

30. Reference Data Sets  In the context of CLIVAR's synthesis, CLIVAR reference data sets and there error fields are required for (1) the analysis of climate processes; (2) for the evaluation of assimilation and WGOMD simulations and (3) as data constraints input to global synthesis.  CLIVAR reference data sets include in situ and satellite data sets, as well as surface flux reference data sets, among others.

31. K ö hl and Stammer (in preparation, 2006) Input Data Sets and Controls

33. Reference Data Sets Examples include:  SST Fields: Reynolds or Pathfinder SST, GHRSST-PP SST Reanalysis  SSH Fields: TOPEX/Poseidon and JASON-1 sea level anomaly from AVISO or PO-DAAC  Time-mean sea surface topography synthesized from drifter data and T/P data (Niiler) and GRACE data.  De-tided tide-gauge data at selected stations with IB correction applied.  Selected WOCE lines and corresponding times P01 (50º N), P03 (25º N), P04 (10º N), P06 (30º S), P14 (dateline). A05 (25º N), A16N (20º W). I03 (20º S), I08N (80º E). TOGA-TAO, BATS, HOT, and Station P time series.  Levitus climatological of temperature and salinity.  Velocity Fields: Surface drifter (Niiler), 900-m float (Davis) velocities; ADCP data.  Surface Flux fields: as defined by white paper of Josey and Smith (2006).

34. CLIVAR Reference Data Sets  Beyond CLIVAR's own needs, climate reference datasets are also required to meet wider needs for climate information (GCOS Implementation Plan (IP), Key Action 23).  In particular the GCOS IP identifies the need for analysed products for all Essential Climate Variables (ECVs) (will be picked up at next GSOP-II meeting).  Given CLIVAR’s responsibilities for the role of the oceans in climate within WCRP, one of CLIVAR’s primary (but indeed not sole) concerns lies in the area of reference datasets for the ocean ECVs and those related to air-sea exchange.

35. Thank You!