Estimated state of ocean for climate research Version:01a
Our 4D-VAR data synthesis system is developed as a part of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC)-Kyoto University collaborative program (known as "the K7 consortium"). The Ocean General Circulation Model is version 3 of the GFDL Modular Ocean Model (MOM3) , which is equipped with several sophisticated schemes; e.g., Noh scheme for mixed layer physics, the Gent and McWilliams (GM) scheme for isopycnal mixing , and quicker advection scheme with major physical parameter values determined through a variational optimization procedure . The horizontal resolution is 1o in both latitude and longitude, with 46 vertical levels spaced from 10 m near the sea surface to 400 m at the bottom. This model is better able to reproduce ocean circulation processes and is expected to form a platform suitable for the use of the 4D-VAR adjoint model. To generate a first guess field, this model was executed by using ten-daily interannual forcings. For the surface momentum, sensible, long/short-wave radiative, and fresh water fluxes in this simulation run, data from the 6-hourly National Centers for Environmental Prediction Department of Energy Atmospheric Model Intercomparison Project (NCEP-DOE-AMIP-Ⅱ) dataset have been used. Latent heat flux was estimated from the NCEP's Optimally Interpolated Sea Surface Temperature (OISST) field by applying the commonly used bulk formulae.
4D-VAR adjoint data assimilation approach is applied [5, 6]. The adjoint codes of the OGCM were obtained using the Tangent linear and Adjoint Model Compiler (TAMC) and the Transformation of Algorithms in Fortran (TAF). In the 4D-VAR approach, optimized 4-dimensional datasets are sought by minimizing a cost function [9,10]. The assimilated elements in this study are temperature and salinity from ENSEMBLES (EN3) dataset which was quality controlled using a comprehensive set of objective checks developed at the Hadley Centre of the UK Meteorological Office . This dataset is largely composed of observations from the World Ocean Database 2005  and supplemented by data from the GTSPP (Global Temperature and Salinity Profile Program) and Argo autonomous profiling floats. In addition of EN3 dataset, recent independent MIRAI RV profiles are simultaneously synthesized. Sea-surface dynamic-height anomaly data derived from high-precision multi-satellite altimetry products distributed by Aviso is also incorporated. All observational data were averaged onto 1o by 1o bins and then compiled as series of 10-day means for the surface data and monthly means for the subsurface data. The control variables are surface fluxes (for net-heat, fresh water, and momentum) and oceanic initial conditions. The assimilation window is 53 years during 1957-2009.
The synthesis of available observations and a pelagic ecosystem model based on nitrogen cycle produces a dynamically self-consistent dataset. Optimized 4-dimensional datasets are sought by minimizing a cost function on the basis of Green's function approach . The assimilated elements are the climatological monthly mean nitrate from WOA05, monthly mean ocean color data from SeaWiFS, and annual mean chlorophyll-a from WOA98 as detritus.
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|Variables, abbreviations||Potential temperature [°C],||tmp|
|Horizontal velocity u[m/s] v[m/s],||vel|
|Surface heat flux [cal/m2/s],||shf|
|Surface freshwater flux [m/s],||sff|
|Wind stress τx[N/m2] τy[N/m2],||tau|
|Dissolved inorganic carbon [μmol/kg],||dic|
|Resolution||Horizontal 1°x1°, Vertical 46 levels|
|Period||1957-2009 (Ver. 01a)|
|File format||Monthly data in netcdf format:
"[XXX]" where "[XXX]" is model variable, "[YYYY]" year, "[MM]" month, and "[VVV]" version, respectively.
Please cite the following data and papers. “YYYY-MM-DD” is date of access.
Satoshi Osafune, Toshimasa Doi, Shuhei Masuda, Nozomi Sugiura, Tadashi Hemmi (2014) Estimated state of ocean for climate research (ESTOC). JAMSTEC. doi:10.17596/0000106 (accessed YYYY-MM-DD)
Osafune, S., S. Masuda, N. Sugiura, T. Doi (2015) Evaluation of the applicability of the Estimated State of the Global Ocean for Climate Research (ESTOC) data set, Geophys. Res. Lett., 42, 12, 4903–4911.
Doi, T., S. Osafune, N. Sugiura, S. Kouketsu, A. Murata, S. Masuda, and T. Toyoda (2015) Multi-decadal change in the dissolved inorganic carbon in a long-term ocean state estimation, Journal of Advances in Modeling Earth Systems, 7, 4, 1885–1990
Masuda, S., T. Awaji, N. Sugiura, J. P.Matthews, T. Toyoda, Y.Kawai, T. Doi, S. Kouketsu, H. Igarashi, K. Katsumata, H. Uchida, T. Kawano, M. Fukasawa (2010), Simulated Rapid Warming of Abyssal North Pacific Waters, Science, 329, 319-322, DOI, 10.1126/science.1188703.
Kouketsu, S., T. Doi, T. Kawano, S. Masuda, N. Sugiura, T. Toyoda, H. Igarashi, Y. Kawai, K. Katsumata, H. Uchida, M. Fukasawa, and T. Awaji (2011), Deep ocean heat content changes estimated from observation and reanalysis product and their influence on sea level change, J. Geophys. Res., 116, C03012, doi:10.1029/2010JC006464.
Masuda, S., T. Doi, N. Sugiura, S. Osafune, and Yoichi Ishikawa (2013), Data Synthesis for Biogeochemical Variables by Using a 4 Dimensional Variational Approach, Earth Simulator annual report 2012.