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EN4: Frequently Asked Questions


1. Which set of corrections should I use for my application?

  • EN4 currently provides two correction schemes; Levitus et al (2009) and Gouretski and Reseghetti (2010). It is recommended that you try using both in your work to see what impact it makes. Note that these correction schemes only correct XBT and MBT data.

2. Is X specific data source in EN4?

  • EN4 takes data from these sources. These sources themselves draw from other sources, it is therefore recommended that you check the information on these four input sources to determine whether EN4 contains the data you are interested in.

3. What are the depth levels in the objective analyses?

  • The specification for the depth levels is contained in the NetCDF files. The quickest way to see them at a glance is to type ncdump -v depth in a linux terminal, if you want the bounds of these levels you can type ncdump -v depth_bnds in a linux terminal. If you are a Windows user then the easiest way to view these variables will be dependent on the software you are using, but once you have your chosen piece of software and a way of reading NetCDF files into it then depth and depth_bnds will still be the variables of interest.
  • Update: You can now see the analysis depth levels and their bounds here.

4. Which temperature and salinity variables are included in EN4?

  • In the profile files we provide observed temperature (TEMP), potential temperature (POTM_CORRECTED) and practical salinity (PSAL_CORRECTED).
  • In the analysis files we provide potential temperature (temperature) and practical salinity (salinity).

5. What is the reference pressure for POTM_CORRECTED?

  • 0 dbar.

6. When are the preliminary files for the previous month uploaded?

  • The preliminary files for the previous month's data are uploaded between the 12th and 18th of the current month. The profile files and analysis files are uploaded at the same time.

7. Can I use EN4 for OHC trend analysis?

  • In the absence of observations the EN4 analyses relax back to a 1971-2000 climatology it is therefore not recommended to use EN4 for trend analysis for long time periods. Time periods after the early 1980s are better suited to trend analysis, though care should always be taken to ensure findings are based on observations and not climatology.

Further questions

If you have any comments or questions about the data which are not answered here, please get in touch.

New versions of the dataset will be released as required to incorporate new features and new historical data. If you have suggestions for changes to the dataset we would love to hear about them.

Funding acknowledgments

The work to produce this dataset was supported by the Joint DECC/Defra Met Office Hadley Centre Climate Programme (GA01101) and by ERA-CLIM, a collaborative project (2011-2013) funded by the European Union under the 7th Framework Programme.


Viktor Gouretski and Franco Reseghetti, 2010: On depth and temperature biases in bathythermograph data: development of a new correction scheme based on analysis of a global ocean database. Deep-Sea Research I, 57, 6. doi:

S. Levitus et al., 2009: Global ocean heat content 1955-2008 in light of recently revealed instrumentation problems. Geophysical Research Letters, 36, L07608. doi:

Obtaining the data

Go to download page
Data are made available without charge for the purposes of private study and scientific research, but please read the terms and conditions.
The latest version of the data is EN.4.2.1. Data from some previous versions of the EN4 dataset are also available. The predecessor of EN4 is available from the EN3 webpages.

Citing the data

When using the data set in a paper, please quote the version number (for example EN4.0.2), the date the data were downloaded and cite the following:

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, 118, 6704-6716, doi:10.1002/2013JC009067

If using a version of the data that incorporate time varying bias adjustments please consider citing the relevant correction scheme paper and please also take note of the data sources used to construct EN4 (described in the paper and available from the download page for each version of the dataset) and acknowledge them appropriately.

Contact us

If you cannot find the information you require on these pages, please do contact us. We are also interested in receiving feedback about the data and its usability. See below if your query is of a commercial nature or relates to the media.

Commercial and media enquiries

You can access the Met Office Customer Centre, any time of the day or night by phone, fax or e-mail. Trained staff will help you find the information or products that are right for you.
Contact the Met Office Customer Centre