GSOP Report

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GSOP Report

• Detlef Stammer
• Universität Hamburg
• CLIVAR/GODAE Synthesis Evaluation Effort
• CLIVAR Reference Data Management Issues

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CLIVARs (WOAPS) Synthesis Needs
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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.

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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.

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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.

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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.

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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.

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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.
  

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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).

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Agenda (1)

• THURSDAY, AUGUST, 31
• 830 Goal of Synthesis Evaluation Effort and
  Charge to the meeting (D. Stammer)
• 845 CLIVAR Data Sets (David Legler)
• 915 CLIVAR Surface Flux Reference Data (Simon
  Josey)
• 945 Discussion of Data and Error Requirements
  (Carl Wunsch)
• SUMMARY of individual Synthesis Projects (10 min.
  each hand outs)
• 1410 Ocean Indices from Data (OOPC, Albert
  Fischer)
• 1430 CLIVAR/GODAE Metrics for Ocean Analysis
  (Detlef Stammer)
• 1450 Data archiving/DODS (Peter Hacker and Paco
  Doblas-Reyes) (10 min. each)
• 1530 Group RMS Model-Data misfits (P. Heimbach,
  D. Menemenlis)
• 1630 Group Meridional Transports (A. Köhl)
• 1730 General Discussion
• 1800 Adjourn

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Agenda (2)

• FRIDAY, SEPTEMBER, 1
• 830 Group Surface Fluxes (L. Yu)
• 930 Group Sea Level Changes (Magdalena
  Alonso-Balmaseda)
• 1000 Group Heat and Salt Content (Anthony
  Weaver)
• 1100 Group Transports through key regions (T.
  Lee)
• 1300 Group Water Masses (K. Haines and T. Lee)
• 1400 Group Indices (A. Fischer)
• 1530 Carbon Program and Synthesis (D. Wallace)
• 1550 General Discussion
• 1630 Summary and Next Steps
• 1700 END OF MEETING

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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.

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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

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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.

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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 Nino12 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.

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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)
• ECMWF
• INGV/ENACT
• CERFACS-LODYC/ENACT
• UK Met Office?
• MERCATOR/MERSEA?
• MOVE-G
• K-7
• BlueLink
• WGOMD and/or IPCC

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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
Bryden et al. (2006)
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ECCO-SIO/50y Ref.
ECCO-SIO
Bryden et al. (2005)
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Max. MOC 25oN
K-7
Bryden et al. (2005)
ECMWF
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Heat/FW transport
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. Seasonal 25N (PW) Atl. Drift 25N (PW/10yr) Global Mean FW 30S (Sv) Global Mean FW 25N (Sv) Model Details Method Details
Ganachaud Wunsch (2000) 1.80 -0.80 0.50 1.30 Macdonald (1998) Macdonald (1998) 0.72 -0.3
AWI LSG 3.5o,Lev adjoint
DEPRESYS
ECCO-JPL 1.45 -1.30 0.44 1.01 0.30 -0.37 0.50 -0.35 MIT 1-1/3o, Lev KPP, GM partition Kalman
ECCO-SIO 1.40 -0.44 0.45 0.96 0.21 0.13 -0.08 0.35 -0.31 MIT 1o, Lev, KPP, GM adjoint
ECCO-50yr 1.26 -0.63 0.38 0.88 0.21 0.14 0.034 0.33 -0.31 MIT 1o,Lev, KPP, GM adjoint
ECCO-GODAE 1.15 -0.78 0.33 0.82 0.21 0.13 0.033 0.55 -0.31 MIT 1o,Lev adjoint
ECCO2-CS510 MIT CS,Lev
ECMWF HOPE 1o,Lev OI
GFDL 1.01 0.22 0.20 0.77 0.31 0.11 -0.018 MOM
INGV 2.2 -1.1 0.7 1.45 0.25 0.11 -0.27 0.82 -0.45 OPA 2-1/2o,Lev, TKE, eddy vel multivar. OI
K-7 MOM3, 1o Lev, KPP,GM adjoint
MOVE
MERCATOR OPA,Lev, TKE SOFA-OI
SODA 0.99 0.16 -0.08 MOM 1-1/3o Lev KPP,GM OI
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Global Heattransport
K-7
GanachaudWunsch(1996)
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Heat transport 25oN
K-7
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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.

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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).

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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 CLIVARs responsibilities for the role of
  the oceans in climate within WCRP, one of
  CLIVARs primary (but indeed not sole) concerns
  lies in the area of reference datasets for the
  ocean ECVs and those related to air-sea exchange.
  

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• Thank You!