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Notes: WORLD OCEAN ATLAS 2018 (WOA18) - prerelease

The WOD18 is an NCEI product and an IODE (International Oceanographic Data and Information Exchange) project.

For any questions about this product, please e-mail OCLhelp desk.


The World Ocean Atlas 2018 (WOA18) release September 30, 2018 updates previous versions of the World Ocean Atlas to include approximately 3 million new oceanographic casts added to the World Ocean Database (WOD) and renewed and updated quality control. The WOA18 temperature and salinity fields are being released as preliminary in order to take advantage of community-wide quality assurance. After release of the previous version of the WOA in 2013 we received a number of communications pointing out suspect features in the released fields. We investigated these features, provided explanations, and when necessary made new quality flagging decisions, resulting in a version 2 of WOA13. We would ask that if people find any suspect features in WOA18, they please e-mail OCLhelp with an explanation of the problem. We will investigate and make any necessary quality decisions before preparing a final WOA18.

The World Ocean Database (WOD) is the world's largest publicly available uniform format quality controlled ocean profile data set. Ocean profile data are sets of measurements of an ocean variable vs. depth at a single geographic location within a short (minutes to hours) temporal period in some portion of the water column from the surface to the bottom. To be considered a profile for the WOD, there must be more than a single depth/variable pair. Multiple profiles at the same location from the same set of instruments is an oceanographic cast. Ocean variables in the WOD include temperature, salinity, oxygen, nutrients, tracers, and biological variables such as plankton and chlorophyll. Quality control procedures are documented and performed on each cast and the results are included as flags on each measurement. The WOD contains the data on the originally measured depth levels (observed) and also interpolated to standard depth levels to present a more uniform set of iso-surfaces for oceanographic and climate work.

The source of the WOD is more than 20,547 separate archived data sets contributed by institutions, project, government agencies, and individual investigators from the United States and around the world. Each data set is available in its original form in the National Centers for Environmental Information data archives. All data sets are converted to the same standard format, checked for duplication within the WOD, and assigned quality flags based on objective tests. Additional subjective flags are set upon calculation of ocean climatological mean fields which make up the World Ocean Atlas (WOA) series.

The WOD consists of periodic major releases and quarterly updates to those releases. Each major release is associated with a concurrent release of the World Ocean Atlas (WOA), and contains final quality control flags used in the WOA, which includes manual as well as automated steps. Each quarterly update release includes additional historical and recent data and preliminary quality control. The latest major release is World Ocean Database 2018 (WOD18). It includes more than 15.7 million oceanographic casts, made up of 3.56 billion individual profile measurements from the second voyage of Captain Cook in 1772 to the modern Argo floats through the end of 2017.

The WOD presents data in netCDF ragged array format following the Climate and Forecast (CF) conventions for ease of use mindful of space limitations. Other formats are available through the WOD web application.