Post on 25-Dec-2015
www.clivar.org
Ocean ReanalysisD. Stammer
• Continued development of ocean synthesis products and reanalysis; some now are truly global, including sea ice, multi-decadal; new EU Arctic reanalysis effort just started.
• Exploration of use of syntheses for initialization.
• Continuation on joint evaluation efforts and improvements.
• Reprocessing of input data sets and prior error information. • 8 Community White paper contributions to OceanObs’09.
• First coupled assimilation efforts exist; more developments are ongoing (K7; GFDL; KlimaCampus, ….).
Ocean synthesis/reanalysis
Ocean synthesis/reanalysis
Annual CLIVAR/GODAE Ocean Synthesis Workshops Intercomparison of products from multiple groups Evaluation of product quality and skill Identification of system strengths and weaknesses Definition of climate-relevant indices and standards for assessment GSOP participation in WCRP Earth System Initialization for Decadal Predictions Workshop, Nov 2009 – KNMI, Utrecht, The Netherlands.
GSOP participation in St. Michaels (MD) Workshop on: Decadal Climate Variability Decadal Climate Predictability and Prediction
WGOMD-GSOP Workshop on Decadal Variability, Predictability and Predictions: Understanding the Role of the Ocean, Boulder, Sept. 2010
Need for Climate-oriented Ocean Data Synthesis
Ongoing Ocean SynthesisOngoing Ocean Synthesis
• Several global ocean data assimilation products are available today that in principle can be used for climate studies. Basin panels were encouraged to enhance their usage.
• Underlying assimilation schemes range from simple and computationally efficient (e.g., optimal interpolation) to sophisticated and computationally intensive (e.g., adjoint and Kalman smoother).
• We need to evaluate the skill of each of those estimates in simulating the true ocean and for initialisation of predictions (EasyInit).
(Trenberth et al.)
SSH Error Sources: instrumental errors
(Trenberth et al.)
Improved Heat Content Estimate
Domingues et al. (2008)
Global Heat Content Anomaly (1022 J)
No Modelz-Level Model
EN3 DePreSys
MITMOMPOPOPA/NEMO
ERA40NCEP
Mercator URDG SODA GFDL GODAS K-7
HOPE
ECMWF INGV
3D-Var/OI 4D-Var.25ox.25o
1ox1o
2ox2o
CORE
GECCO
Bias corr.E-P.
Relax.
Relax.
Relax.Relax.QSCATGPCP
DATADATA
Example: The GECCO State Estimate
• Part of the ECCO Consortium Effort (see ecco-group.org).• Ocean synthesis, performed over the period 1952 through 2001 on
a 1º global grid with 23 layers in the vertical, using the ECCO/MIT adjoint technology (now extended to present globally).
• Optimization started from Levitus and NCEP forcing and uses state of the art physics modules (GM, KPP).
• The models adjoint (obtained using TAF) is used to bring the model into consistency with most of the available ocean observations over the full period by adjusting control parameters.
• So fare control parameters: initial temperature and salinity fields, surface forcing. Now also included: mixing parameters.
• Note: the final run is a free forward run.
Comparison GECCO - ObservationsComparison GECCO - Observations
Topex/Poseidon (1993-2001)GECCO Model (1992-2001)
(Köhl et al., 2007)
Total Trend 1992 – 2001 (cm)
Halosteric Trend
Thermosteric Trend
Steric Trend
GECCO
ECCO-SIO/50y + Ref.
Bryden et al. (2005)
Ocean synthesis/reanalysis
12m-rm seasonal anom: NATL Averaged temperature over the top 300m
1950 1960 1970 1980 1990 2000Time
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
ukdpukoicfcs2cfas2ecco50y
gfdlsodaecmfaecmfcukgs
ingvmri-eccoSIOcfasamct2
mct3eccoJPLaeccoJPLceccoMITGMAO
sdv ensm = 0.164s/n ensm = 1.620
sdv all = 0.206s/n all = 2.028
spread = 0.101
N. Atlantic Temp(0-300 m)
WCRP enablinginitialized predictions
Global Synthesis and Observations PanelIntercomparison of the Indonesian Throughflow (ITF) Transport Estimated by
Ocean Data Assimilation (ODA) Products (Joint GSOP-IOP activity)
• No substantial weakening associated with the 1976 “climate shift”: Wainwright et al. (2008) reported a 2.5-Sv reduction based on an analysis of IX1 XBT data (Fremantle – Sunda Strait).
• Decadal signals of 10-15 year periods.• A consistent strengthening during 1992-2000: consistent with observed wind and SSH
Five-year low-pass ITF transport
anomaly (color curves) and their
ensemble average (14 synthesis
products) (black curve)
SODAECMWF GECCO
SODA ECMWFGECCO
Trend in Sea Level 1992-2001 (cm/yr)
SODA
ECMWF GECCOSODA
ECMWF
ECMWFGECCO
GECCO
Trend in Sea Level 1962-2001 (cm/yr)
Next GSOP Efforts
• Chairs: B. Sloyan, K. Haines (WOAP member), D. Stammer
• Implementation of OO’09 Outcome (jointly with OOPC)
• Reanalaysis of global historic hydrography
• Reanalysis of XBT data
• Analyze global budgets and sea level
• EazyInit: Providing initial conditions for seasonal- to decadal predictions.
• Improving initial conditions and initializations.
• Preparing for Coupled Data assimilation
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Thank you