Ocean temperature and salinity from EN4
Topics
- Access
- Description
- Parameters
- Coverage, spatial and temporal resolution
- Data quality
- Contact person
- References
- Data citation
Access
RESTRICTED: This link to the data set is only available for a restricted user group. The data set is only accessible in CEN/MPI net or accessible from external nets with a customer account. Please contact ICDC if you would like to access this data from outside the network.
- View salinity and temperature data at LAS
- Access salinity and temperature data via OPeNDAP
- Data access via file system: /data/icdc/ocean/en4/
Description
This global data product of the subsurface ocean temperature and salinity EN4 (version 4.2.2) is based on data of all instruments capable of profiling the water column. Main data source is WOD18; the three other principal data sources are data from the Arctic Synoptic Basin Wide Oceanography (ASBO), Global Temperature and Salinity Profile Program (GTSPP, since 1990) and Argo Data (since 2000) (see literature and EN4 websites in the references).
The data were first cleaned from double profiles (Gronell and Wijffels, 2008). Subsequently, a large number of quality assessment and enhancement steps were performed. Many of these were also applied in the older versions of this data set (e.g. Ingleby and Huddleston, 2007, and references therein), but some of these were specifically developed for version 4 of this data set (Good et al., 2013). By using Objective Analysis the enhanced and cleaned profiles were interpolated to the gridded data set offered. In addition, in contrast to earlier version of the data set, estimates about the uncertainties of the Objective Analysis are provided together with temperature and salinity values (Good et al., 2013). (see references)
We only offer data (gridded and profiles), which were bias-corrected following the method of Gouretski and Cheng (2020). Note: this is one of the major updates compared to Version 4.2.1 and has been realized for the so-called ".g10" flavour of this data set. In addition T10 XBTs were corrected. For data where a different bias correction was applied (e.g. ".c14") , we refer to the Download Website EN4 at Met Office Hadley Centre (see references).
Last update of data set at ICDC: November 2, 2023.
Parameters
| Name | Unit | Comment |
|---|---|---|
| Temperature | K | |
| Salinity | 1 | |
| Temperature error standard deviation | K | No values below 1000m water depth |
| Salinity error standard deviation | - | No values below 1000m water depth |
| Temperature observation weights | - | |
| Salinity observations weights | - |
Coverage, spatial and temporal resolution
Period and temporal resolution:
- 1900-01 to 2023-08
- Monthly (note: the data set is updated monthly at the original data provider)
Coverage and spatial resolution:
- Global
- Spatial resolution: 1.0° x 1.0°, kartesian grid
- Geographic latitude: -83.0°N to 89.0°N
- Geographic longitude: 1.0°E to 360.0°E
- 42 depth levels from 5.0 m to 5350 m water depth
- Dimension: 360 columns x 173 rows x 42 depth levels
Format:
- NetCDF
Data quality
Since version (v4) the subsurface ocean temperature and salinity data set is the first one which contains an uncertainty estimation of the Objective Analysis method. These uncertainty values, for temperature and salinity, are however only available for depths above 1000 m, i.e. between ~5 m and ~1000m (see parameters).
The considerable number of biases caused by the large variety of instruments and profiles included in this data set can be and has been corrected with a number of different approaches (see references). We only offer the product (here: ".g10") for which the new bias correction after Gouretski and Cheng (2020) has been applied. Note that compared to Version 4.2.1 data from eight TAO buoys between 2015 and 2016 were removed; the same applies to a single year Argo float being stuck at depth.
We refer to the webpage https://www.metoffice.gov.uk/hadobs/en4/download-en4-2-2.html and the literature in the references for more information about error sources and their relevance for the data set as well as about the applied bias-corrections and quality improvements. Warnings about eventual inconsistencies found after product release may also be found at the websites of EN4 at Met Office Hadley Centre (see references).
Contact
Rachel Killick
MetOffice, Exeter, U.K.
email: rachel.killick (at) metoffice.gov.ukStefan Kern
ICDC / CEN / University of Hamburg
email: stefan.kern (at) uni-hamburg.de
References
Literature:
- 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, J. Geophys. Res.-Oceans, 118, 6704-6716, https://doi.org/10.1002/2013JC009067
- Gouretski, V., and F. 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 Res. I, 57, 812-833, https://doi.org/10.1016/j.dsr.2010.03.011
- Gouretski, V., and L. Cheng, 2020: Correction for Systematic Errors in the Global Dataset of Temperature Profiles from Mechanical Bathythermographs. Journal of Atmospheric Technology and Oceanic Research, 37, 5, https://doi.org/10.1175/JTECH-D-19-0205.1
- Cheng et al., 2014: Time, Probe Type, and Temperature Variable Bias Corrections to Historical Expendable Bathythermograph Observations. Journal of Atmospheric and Oceanic Technology, 31, 8, https://doi.org/10.1175/JTECH-D-13-00197.1
- Cowley et al., 2013: Biases in Expendable Bathythermograph Data: A New View Based on Historical Side-by-Side Comparisons. Journal of Atmospheric and Oceanic Technology, 30, 6, https://doi.org/10.1175/JTECH-D-12-00127.1
- Levitus, S., et al., 2009: Global ocean heat content 1955-2008 in light of recently revealed instrumentation problems, Geophys. Res. Lett., 36, L07608, https://doi.org/10.1029/2008GL037155
- Gronell, A., and S. E Wijffels, 2008: A semiautomated approach for quality controlling large historical ocean temperature archives, J. Atmos. Ocean. Technol., 25(6), 990-1003, https://doi.org/10.1175/JTECHO539.1
- Ingleby, B., and M. Huddleston, 2007: Quality control of ocean temperature and salinity profiles - historical and realtime data, J. Mar. Syst., 65, 158-175, https://doi.org/10.1016/j.jmarsys.2005.11.019
Websites:
- EN4 at Met Office Hadley Centre, https://www.metoffice.gov.uk/hadobs/en4/index.html
- Download EN4 at Met Office Hadley Centre, https://www.metoffice.gov.uk/hadobs/en4/download-en4-2-2.html
- Profile file format
- Analysis file format
- Met Office Hadley Centre observations datasets, EN4 quality controlled ocean data: EN4.2.2 data sources and acknowledgements, https://www.metoffice.gov.uk/hadobs/en4/en4-2-2-data-sources.html
Data citation
Please cite the data as follows:
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
EN.4.2.2 data were obtained from https://www.metoffice.gov.uk/hadobs/en4/ and are © British Crown Copyright, Met Office, [last access: October 30, 2023], provided under a Non-Commercial Government Licence http://www.nationalarchives.gov.uk/doc/non-commercial-government-licence/version/2/.
In case time varying bias corrections have been applied, we kindly ask you to also cite the respective reference - in our case the paper by Gouretski and Cheng (2020) (see references).
Finally, please take a note of the data sources (see http://www.metoffice.gov.uk/hadobs/en4/en4-2-2-data-sources.html ) and mention them in the acknowledgements.