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A reanalysis of
ocean climate

Goal The goal of SODA is to reconstruct the historical physical (and eventually biogeochemical) history of the ocean since the beginning of the 20th century. As its name implies, the Simple Ocean Data Assimilation ocean/sea ice reanalysis (SODA) uses a simple architecture based on community standard codes with resolution chosen to match available data and the scales of motion that are resolvable. Agreement with direct measurements (to within observational error estimates) as well as unbiased statistics are expected. While SODA remains a university-based research project, we want to be helpful to potential users by providing a reliable, well-documented, source of seasonal climate time-scale ocean reanalysis to complement the atmospheric reanalyses available elsewhere (NOAA/EMC, NASA/GMAO, and ECMWF, for example).

SODA3 (SODA Version 3) is the latest release of SODA. The model has been switched to GFDL MOM5/SIS numerics with eddy permitting 1/4°x1/4°x50lev resolution (28km at the Equator down to <10km at polar latitudes) . This model is similar to the ocean component of the GFDL CM2.5 coupled climate model, and includes the same SIS1 active sea ice model. A number of improvements have been included in the sequential DA filter, but SODA3 still has a pre-specified flow-dependent error covariance. We now offer an ensemble set of ocean reanalyses, the spread of which provides information about uncertainty. A description of SODA3 and its comparison to SODA2 is now available as Carton, Chepurin, and Chen (2018).

Bias correction: One of the focusses for SODA3 has been to identify, quantify, and hopefully limit sources of bias. A major source of bias is in the forward model that predicts the evolution of the flow. A major (but not the only) source of model bias, in turn, is introduced through bias in the meteorological fluxes (heat, freshwater, and momentum). To address this problem SODA3 is actually an 'ensemble' of reanalyses (Table 1), the spread of which contains information about the dependence on surface forcing. Many of these ensemble members are driven by fluxes that have been bias-corrected as discussed in a recent paper (see the reference list).

Table 1 Partial list of available reanalysis ensemble members (see SODA tab above for a full list and to access the data). In the naming convention the second number identifies the source of the meteorological forcing. The third number (1 or 2) identifies the bulk formula used to compute thermodynamic fluxes. A '0' at the end of the name indicates that it is a simulation. A readme file available under the SODA tab provides more information on naming conventions, file structures, etc.

SODA3.3.1.0NO MERRA-2* Large-Yeager 1980-2015
SODA3.3.1YES MERRA-2* Large-Yeager 1980-2015
SODA3.3.2 YES MERRA-2*COARE41980-2016
SODA3.4.1.0NO ERA-I*Large-Yeager 1980-2015
SODA3.4.1YES ERA-I*Large-Yeager 1980-2015
SODA3.4.2YES ERA-I*COARE41980-2016
SODA3.6.1YES CORE2Large-Yeager 1980-2009
SODA3.7.2.0NO JRA-55*COARE41980-2013
SODA3.7.2YES JRA-55*COARE41980-2016
SODA3.11.2.0NO DFS5.2COARE41980-2015
SODA3.11.2YES DFS5.2COARE41980-2015
(* indicates we have applied flux seasonal bias correction. )

Missing files 23 October, 2017 -- we lost some of the original ocean and sea ice 5dy files (none of the regridded files) due to our misinterpretation of the disk scrubbing policy on Yellowstone. The missing files for each experiment are listed here.

Future Hopefully sometime this year (2018) we will get to the first half of the 20th century, begin to encorporate quasi-isopycnal dynamics, an improved error covariance, enhanced resolution, and introduce ocean biogeochemistry. Well, maybe not all that. We expect the next major revision of SODA to be part of a partially or fully coupled atmos/ocean/ice reanalysis.

For additional information send us email: Gena Chepurin and Jim Carton. If you don't get a response, we've gotten distracted. Please keep trying!

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Acknowledgements SODA relies on extensive collaborations. In addition to the National Science Foundation Physical Oceanography Program we owe debts to: NOAA/GFDL, NOAA/NCEP, NOAA/NESDIS (especially the Laboratory for Satellite Altimetry and NCEI), NASA/GMAO, and the NASA MAP and Physical Oceanography programs. Many individuals have contributed to SODA including: Tim Boyer, Gil Compo, Dick Dee, Eric Hackert, Sirpa Hakkinen, Sasha Ignatov, Eugenia Kalnay, Syd Levitus, Matt Maltrud, Julie McClean, Laury Miller, Steve Penny, R. Raghunath, James Reagan, Tony Santorelli, Mike Steele, and most notably Ben Giese, Xianhe Cao, and Hank Seidel.

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