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EN4.2.0 quality controlled ocean data: Analysis files

Analysis files

The analysis files contain objective analyses produced using optimal interpolation of the profile data for a particular month and a persistence forecast background. The analyses are produced on a regular 1 degree latitude/longitude grid and have 42 levels in the vertical. To reduce storage space not all latitudes are saved in the files. The files also contain an estimate of the analysis error standard deviation and an 'observation influence' analysis. The latter is an analysis formed by setting all observation values to one and all background values to zero when calculating the analysis. The resulting fields have numbers between 0 and approximately 1. If the number is close to one it means that observations have closely influenced the analysis while a zero indicates that no observations were available during the month in that location.

The table below describes the variables in the NetCDF files.

NetCDF variable Description
depth The depth of each level (m).
lat The (centre) latitudes of the grid points (degrees).
lon The (centre) longitudes of the grid points (degrees).
time The middle of the month that was analysed.
time_bnds Contains the beginning and end times of the month that was analysed.
temperature The potential temperature at each grid point.
salinity The salinity at each grid point.
temperature_uncertainty The analysis error standard deviation of the potential temperature analysis.
salinity_uncertainty The analysis error standard deviation of the salinity analysis.
temperature_observation_weights The relative weighting given to the observations compared to the background in the potential temperature analysis.
salinity_observation_weights The relative weighting given to the observations compared to the background in the salinity analysis.

More information

Please read:

Good, S. A., M. J. Martin and N. A. Rayner, 2013. EN4: quality controlled ocean temperature and salinity profiles and monthly objective analyses with uncertainty estimates, Journal of Geophysical Research: Oceans, doi:10.1002/2013JC009067

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