This global data product of the subsurface ocean temperature and salinity EN4 (version 4.2.0) is based on data of all instruments capable of profiling the water column. Main data source is WOD13; 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 http://www.metoffice.gov.uk/hadobs/en4/en4-0-2-data-sources.html ).
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).
We only offer data (gridded and profiles), which were bias-corrected following the method of Gouretski and Reseghetti (2010). For data where a different bias correction was applied, we refer to http://www.metoffice.gov.uk/hadobs/en4/download-en4-2-0.html.
Last update of the data set at ICDC: Oct 26, 2017.