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GECCO2

Access

UNRESTRICTED

Nov 27, 2015 New Version online that replaced the previous one: Since the year 2014 used a wrong scaling factor for precipitation, the last assimilation window 2011-2014 was repeated after correcting the error.

Interpolated fields on a regular 1x1° grid: OPeNDAP / HTTP, FTP, View in LAS

Fields on the native model grid: HTTP, FTP
Warning: Do not use the grid information inside the single cdf-Files but the grid from the file "grid.cdf"

RESTRICTED only accessable in CEN/MPI net or via CliSAP login  What does that mean?

Data access via file system: /data/icdc/ocean_syntheses/GECCO2

 

Description

The GECCO2 ocean synthesis is the German contribution of the Estimating the Circulation and Climate of the Ocean project (ECCO, www.ecco-group.org). The synthesis uses the adjoint method to adjust the initial temperature and salinity in 1948 together with the air temperature, humidity, precipitation, and zonal and meridional wind every 10 days to bring the model into consistency with the data, which derive from the EN3v2 data base  AVISO along track SLA , GOCO mean dynamic topography, HadISST, AMSRE SST, and the WOA09 climatology.   The global model is based on the MITgcm model, has 50 levels, and uses zonally 1 degree and meridionally varying higher resolution. The background atmospheric state is taken from the 6 hourly NCEP/NCAR Reanalysis 1.

The GECCO2 synthesis covers the period 1948-2011.  For the last iterations, the synthesis was partitioned into overlapping 5 year windows.   Since only the initial condition in 1948 is allowed to change in GECCO2, the atmospheric state is the only control for all windows except for the first one. The synthesis was extended twice, into the year 2013 and 2014, respectively, by taking the initial conditions of iteration 28 from the end of 2008.

Model: MITgcm
Resolution: 1x1/3°, 50 z-levels, partial cells
Data assimilated: EN3_v2a T/S (XBT corrected)+ AVISO along track SLA , GOCO MDT, HadISST, AMSRE SST, WOA09 climatology
Assimilation method: 4D-VAR (adjoint) method
Forcing and relaxation used: NCEP RA1 atm. Fields, Bulk formulae, Large and Yeager, 2009

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Parameters

Name Unit filename
water temperature deg C temp*
sea surface height m zeta*
salinity g/kg salt*
net shortwave flux W/m^2 qsw*
totel heat flux W/m^2 qnet*
fresh water flux kg/s/m^2 emp*
meridional wind stress N/m^2 fv*
zonal wind stress N/m^2 fu*
u velocity m/s u*
v velocity m/s v*
w velocity m/s w*
bottom pressure Pa bp*
effective sea ice thickness m heff*
sea ice area % area*
meridional ice velocity m/s vice*
zonal ice velocity m/s uice*

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Coverage, spatial and temporal resolution

Period and temporal resolution:

  • 1948-2014
  • monthly

Coverage and spatial resolution:

  • Global
  • Spatial resolution: 1°x1° (interpolated product)
  • Dimension: 360x180x50
  • Altitudes: 50 depth levels

Format:

  • netCDF4
     

Data quality

Variational method fit the trajectory best during the middle section of the assimilation period. Due to the separation of the run into 5 year long  windows with one year overlap, adjustments show some dependence on the time within each window, which are noticeable in regions of stronger adjustments, particularly at the latitudes of the strong western boundary currents. Despite the initial iterations that cover the whole period, a four year periodicity of the corrections results from this dependence of the adjustment that affects interannual variability.

Further information about the 4-year-cycle can be found in this PDF document.

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Contact

Armin Köhl: armin.koehl (at) uni-hamburg.de

Remon Sadikni (ICDC): remon.sadikni (at) uni-hamburg.de

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References

Köhl, A. (2015), Evaluation of the GECCO2 Ocean Synthesis: Transports of Volume, Heat and Freshwater in the Atlantic, Q. J. R. Met. Soc., 141(686), 166-181, doi: 10.1002/qj.2347


Data Citation

Please contact Armin Köhl: armin.koehl (at) uni-hamburg.de

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