World Ocean Circulation Experiment
Global Data Resource
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What is the structure of the disks?
There are 2 DVDs, each of which contain a series of folders (also known as directories) of 650MB or less in size.† At the top level of both of the DVDs (the "root" directory) are identical copies of the introductory files that you are looking at now. From these introductory pages you can find tools such as a search engine to locate data files, software you might need to view the browser pages or unzip files, and some help files.† Below this level are more folders (directories) containing the data files and documentation for a variety of WOCE data types.† The introductory browser pages include links to each data folder, where an index or welcome page allows you to explore their contents.†
What kind of information can I find here?
The data on these disks are high quality oceanic measurements made from a variety of instruments including ships, free-roaming instruments, moored platforms and satellites. The data cover most of the global ocean and the majority of the data are from the period of 1990 to 1998, the intensive observation phase of WOCE. Some data are included before and after this period to provide a longer term context for the WOCE period.† All data are accompanied by documentation that explains collection and quality control procedures.† Where possible the individuals and organisations that collected the data are identified.
Are the data free?
Yes!† You may use the data on these disks as you choose to.† We only ask that you acknowledge the source of the data in any publications.† This may mean acknowledging the principal investigator of a particular project, and by citing the reference for these disks:
WOCE Data Products Committee, 2002: WOCE Global Data, Version 3.0, WOCE International Project Office, WOCE Report No. 180/02, Southampton, UK.
How do I acknowledge the WOCE programme as a data source?
We encourage all users to acknowledge the many individuals and organisations that contributed to WOCE and the data resource that you are using.† You can do this either by acknowledging the originators of the data (given in the documentation where possible), or by citing this DVD set as a reference.† The full reference to use is:
WOCE Data Products Committee. 2002. WOCE Global Data, Version 3.0, WOCE International Project Office, WOCE Report No. 180/02, Southampton, UK.
Is there a list of WOCE publications?
The list of refereed publications and "grey literature" (not peer reviewed) arising from WOCE was still growing as these disks were finalised, but the list to date is given in the WOCE Bibliography.
What were the aims of WOCE?
WOCE was one of the principal projects of the World Climate Research Programme. It was the first attempt to survey the oceanic circulation globally over a brief period, aiming to collect a data base to support the development of the global eddy-resolving ocean circulation models for use in climate research. Such models became feasible during WOCE as computer power increased. WOCE also studied the inherent variability of the ocean during the 1990s. The WOCE data set will form a high quality baseline against which future and past change can be assessed.† The goals of the experiment were laid out in the Science Plan and the projects origins are described in Chapter 1.3 of the book “Ocean Circulation and Climate – Observing and Modelling the Global Ocean”.† WOCE also aimed to identify cost-effective methods of monitoring the ocean.† Two immediate legacies are the data from altimeter satellites and the growing array of Argo profiling floats.
What was the observation strategy?
The scientific rationale for the observation strategy was set out in the Implementation Plan which described three Core Projects; 1) the Global Description, 2) the Southern Ocean, and 3) the Gyre Dynamics Experiment. The field programme for those Core Projects was set out in terms of the required observations; a grid of hydrographic sections, locations of current meter moorings, coverage of surface drifters and subsurface floats, locations of sea-level stations, and optimum sampling routes for XBTs (eXpendable BathyThermographs).† Supporting all these in situ measurements were the global satellite missions.† Countries with national WOCE funding were invited to state which parts of the field programme they would do, while the Data Information Unit (DIU) kept track of the commitments and activities.† The SSG (Scientific Steering Group), its sub-committees and the IPO (International Project Office) co-ordinated the field programme to ensure all critical observations were made and that effort was not unnecessarily duplicated.
What were the different parts of the field programme?
Broadly speaking the field programme was designed with available and developing measurement techniques in mind.† The heart of the programme was a global grid of hydrographic sections; a series of lines across the ocean basins along which closely spaced stations sampled the water column from top to bottom for a variety of physical and chemical parameters.† The global grid was designed so that each section was sampled once to the highest quality (the Hydrographic One Time Survey).† Some of the sections and stations were repeated seasonally and/or annually to describe temporal variability (the Repeat Hydrography and Time Series Stations).† Together those aspects made up the WOCE Hydrographic Programme or WHP. Associated with the hydrographic section were underway measurements of Bathymetry, Shipboard ADCP (Acoustic Doppler Current Profilers), Sea Surface Salinity and sea surface Meteorology.†
At specific locations direct current measurements were required from Moored Current Meter Arrays, and neutrally buoyant Subsurface Floats were deployed to roam at depth to reveal deep circulation patterns.† Towards the end of WOCE, subsurface floats were developed with a capability to measure temperature and salinity during their ascent through the water column, the Profiling Floats.† Surface Drifters were deployed in great numbers to measure the surface wind driven circulation (the Surface Velocity Programme).† Sea Level Stations with tide gauges provided data to calibrated sea surface height measurements from satellites (altimetry), to measure long-term changes in sea level and to record flow through straits. And finally, Voluntary Observing Ships (merchant, navy and fishing vessels) were utilised to deploy thousands of XBTs (eXpendable BathyThermographs) for the Upper Ocean Thermal programme to look at heat content and seasonal to interannual variability.
Who ran the experiment?
The Scientific Steering Group (SSG) oversaw the scientific development of WOCE, meeting once or twice a year at locations around the world.† The SSG was made of scientists from many of the countries involved in WOCE, with members and chairmen rotating off the committee after 2 to 6 years of service. Long term continuity was provided by the International Project Office (IPO) based in the UK, which co-ordinated the implementation of the experiment.†
How much did it all cost?
The International Project Office has estimated that the total cost of WOCE, excluding the supporting satellite missions, was in the region of US$1 billion over 10 years. †This estimate includes the cost of the field programme (including new ships and instrumentation), the data management system, and analysis of the data in laboratories and institutions.† All this funding came from national agencies supporting the programme for climate research.†
Who was involved in the experiment?
Nearly 30 countries, numerous funding agencies and countless individuals took part in this the biggest oceanographic experiment to date.† Each data stream here on the DVDs provides documentation about who provided the data.
When was it done?
The planning for WOCE began in the early 1980's when the concept was first presented to the scientific community.† The Scientific Steering Group (SSG) first met in 1983, the Science Plan was published in 1986 and the Implementation Plan (which described the practicalities of meeting the programme objectives) was published in 1988.† The intensive observation phase began in January 1990 and lasted until December 1998.† Following the field programme came the Analysis, Interpretation, Modelling and Synthesis phase which ended in 2002.†
Where can I find documentation on the design of WOCE?
What do you mean by "data resource"?
We refer to the WOCE Data Resource because the product you are using is more than just a data set.† Of course it contains the data from the WOCE field programme, but more than that, it includes extensive documentation, quality assessment information for each data file, high quality scientific products, and tools for searching the large variety of data collected under WOCE auspices.
Is this all the WOCE data?
The Data Information Unit which tracked the field programmed and monitored the data system has estimated than more than 90% of all data collected under WOCE are present on these 2 DVDs.† The remaining 10% include some good data that were not submitted, but also some effectively unusable; data with uncorrectable errors, or data collected but for which no resources were available for processing.† This remarkable achievement reflects the dedicated work of the data assembly centres, and the community spirit of scientists and technicians for whom making data available to the wider community became a priority.†
What were the WOCE data streams?
The WOCE data system was designed around the measurement techniques that formed the field programme. Each type of data, a "data stream", was accumulated at a Data Assembly Centre that had specialist knowledge of the particular kind of data.† The data streams that made up the WOCE data system were:
Hydrography (from the WOCE Hydrographic Programme or WHP, which included the One Time Survey, Repeat Hydrography and Time Series Stations).
Shipboard ADCP (Acoustic Doppler Current Profilers, collected on hydrographic cruises)
Surface Meteorology (collected on hydrographic cruises)
Current Meters (from moored current meter arrays)
Drifters (from the Surface Velocity Programme)
Floats (neutrally buoyant subsurface floats)
Profiling Floats (a particular variety of floats that collected temperature and salinity profiles)
Upper Ocean Thermal (data from eXpendable BathyThermographs or XBTs)
Satellite Sea Level (also known as Sea Surface Height or Altimetry)
Sea Level (from tide gauges; stage 1: Fast Delivery)
Sea Level (from tide gauges; stage 2: Delayed Mode)
Satellite Sea Surface Temperature
Satellite Surface Winds
Sea Surface Salinity (from thermosalinographs and buckets)
Bathymetry (ocean depth, collected on hydrographic cruises)
In addition, two Special Analysis Centres (SAC) were formed to generate scientific products from the data streams.† They were a Hydrographic SAC which produced gridded fields from the hydrography data, and the Surface Fluxes SAC which concentrated on generating air-sea flux products from meteorological data.
Were there WOCE standards for data collection?
Yes, WOCE revolutionised the science of oceanography by insisting on the highest quality measurements possible.† Details of required accuracy and precision for most of the parameters collected on hydrographic cruises were set out in the WOCE Hydrographic Programme (WHP) Manuals.† For many scientists and technicians this meant the purchase of new equipment and the acquisition of new skills and techniques.† Those manuals are reproduced in the Hydrography Folders on Disk 1.† In addition, the process of scientific quality assessment of data by the Data Assembly Centres, combined with feedback to data providers, led to an increase in the skills required to collect data of the highest quality.
How can I be sure of the quality of the data?
The majority of WOCE data have had some level of quality control applied to them, and all have accompanying documentation to explain the procedures and "flag" system (a flag is a marker to indicate the level of quality assigned to a data file or data point).† The exceptions are the float profiles and sea surface salinity data sets, both of which relied on the data originator's quality assessment.† Most WOCE data have been though stringent scientific quality control procedures to ensure that you can be confident of the quality of the data.† The introductory pages on this disk provide an overview of the quality control for each variety of data.
Were there WOCE standards for data format?
Throughout WOCE each Data Assembly Centre stored and distributed data in its own format since it was agreed to be impractical and foolhardy to attempt a standard WOCE format to fit all kinds of data.† The result was that users needed a different piece of software to read the data from each data stream that made up the data resource.† However in 1999 the WOCE Data Products Committee that was designing and producing the second version of the WOCE Global Data (on Compact Disks) decided to use a binary format called netCDF.† The advantage of netCDF was that it was self-describing, which means that each data type could have its own fields and units, but that software designed to read netCDF files could immediately recognise what they were. In effect a user could use one kind of software to read all the files that were in netCDF.
The use of netCDF was further improved for this Version 3.0 of the WOCE Data Resource. Not only are all data files in netCDF, but some internationally recognised standards for netCDF files have been implemented, meaning the data are readable through many commonly used software packages.† More details about netCDF are given in the Data Format section of these FAQs.
Who produced the Data Resource?
The product you are using now was designed and constructed by the WOCE Data Products Committee which consisted of WOCE scientists and data managers from all the WOCE Data Assembly Centres.† The Data Products Committee was formerly known as the WOCE Data Management Committee and was one of the longest running committees of the project, meeting 15 times between 1989 and 2002.† Version 1.0 (on CDs) was produced in 1998 for the WOCE Conference in Halifax, Canada.† Version 2.0 (on CDs) was published in 2000 as an interim product, and Version 3.0 (2002) is the final product.
What is the layout of the DVDs; how are the data arranged?
The data are arranged on the disks by the elements of the field programme under which they were collected.† There are folders (directories) for each data stream that contain the data and documentation in a series of smaller folders (subdirectories). You can reach those folders in your browser from the introductory pages you are looking at now; click on the links on the left hand side of the screen.
What is the content or granularity of each data file?
Each data stream has a specific amount of detail in individual files; this is sometimes referred to as the "granularity" of the data file.† For example, it is natural for a single hydrographic station to be in a single file, but may be more appropriate for a day's worth of data to be in a single file for measurements collected while the ship is steaming, e.g. surface meteorology. The table below lists the granularity of each data stream.
How can I search for data?
There are two ways for you to proceed.† You can use the integrated WOCE search tool (link) to search inventories of the data files for data in a particular geographic location, in a certain time period, or that contains specific variables. If you wish to find all data from a particular cruise you can search using its unique identifier, the ExpoCode.† Alternatively you can use your browser to look at the individual data stream folders to look for data from a particular current meter array, or sea level station etc. (click on the links on the left hand side of this page).†
What are the inventory tables?
Each data stream includes at least one inventory table of its data filenames.† The inventories are text files that can be opened in any spreadsheet or word processing package, though some are very large.† There is one line (or row) per file, and a variety of fields (or columns) that specify the location of the file, the time and position ranges of the data file, and the parameters that it contains.† For the data streams with the largest number of files, there are several inventory tables to make them a manageable size.† All inventory tables contain the same fields for file location, data position and time, but they may contain a variety of fields for the data parameters.† A space in the table means the data file does not contain that particular parameter.
The inventories were developed for use with the integration search tool provided on the DVDs, but could be used with your own software.† The inventories contain only data that were labelled as "good" by the WOCE quality control procedures.† This means that data regarded as suspect or bad which are included on the DVDs are not listed in the inventories.
What information is provided by the search tool?
The search tool will provide you with the names of data files that meet your specified criteria. It will also provide the pathname for the location of the data file on the disks.† If the data file is contained within a zipped file, then the names of both the zipped file and the expanded data file name are given.
What are the limitations and pitfalls of the search tool?
- The search tool does not provide you with a html link to the data files on these DVDs; you will need to follow the pathnames manually or write a program or executable script to access the files automatically.
- If you include global fields such as satellite files in a geographical search you will get all those global file names returned to you.†
- There are vast numbers of profiles in the Upper Ocean Thermal data stream (XBT or eXpendable BathyThermograph temperature profiles).† The inventory has been designed to search for the zipped file (each ocean basin per year-quarter) which matches your criteria.† There is a good chance that you will end up with more data than you need if you are searching for a small area.
- If you need data from a single hydrographic cruise, find the correct ExpoCode from the master list and search on that.† The match must be exact if you use the full ExpoCode, so if in doubt, use just the first few characters.
- The search tool will only return the names and locations of netCDF data files.† It will not tell you if an ASCII version of the data file exists on the DVDs, and it will not tell you where the documentation associated with the data can be found.
- The returned filenames will satisfy your criteria, but may not give you any indication of which cruise, date or dataset it came from.
- The inventories only include data that are flagged as good (i.e. have passed quality control tests).† This means that if you are looking for extremes in a particular parameter, or if the position or time information was considered suspect in the data, then you will not be given those filenames.†
I can't make the search tool work, what do I do now?
Donít worry, the data are still available to you.† You can search the inventories using your own software, though some of the tables are very large and manual searches will probably be slow.† The tables are present on the DVDs as individual files so you can search one at a time. You can also explore the data stream folders (directories) on the disks using your browser (click on the links on the left hand side of this page).† Each data stream has summary tables that direct you to the data files.†
How can I find all the data from a single cruise?
The easiest way is to use the WOCE integrated search tool to search on the cruise ExpoCode. Each hydrographic cruise was assigned a unique code, and all data from a particular cruise can be identified with that ExpoCode.† Alternatively, use your browser to look for the ExpoCode in the summary tables provided for each data stream from the hydrographic cruises (click on the links on the left hand side of this page).†
What is an ExpoCode and is there a list of them somewhere?
An ExpoCode is a unique identifier assigned to each of the WOCE hydrographic cruises. Many data streams were not directly associated with the hydrographic cruises and therefore do not have ExpoCodes. The data streams that do have ExpoCodes are Hydrography, the Shipboard ADCP (Acoustic Doppler Current Profilers), and the surface Meteorology.
The code is made up of country code and ship code (always the first 4 characters) followed by cruise number, though the format of the latter is not consistent. Cruises with more than one leg have an underscore and extension. For example, for code 06MT30_1, the "06" means Germany, "MT" identifies the ship the Meteor, "30" indicates cruise number 30, and "_1" means Leg 1. The complete list of ExpoCodes with the section, ship and chief scientist is available on the Help pages.
How do I access the data and documentation?
The data can be accessed using your browser to follow the links though the data stream folders (click on the links on the left hand side of this page).† Alternatively, by using the pathnames and filenames provided by the WOCE integrated search tool you can go directly to the data files using your own software packages. All data are provided in netCDF and you will need special software to read the data; this is explained in the "What is the Data Format" section of these FAQs, and on the Help pages of this DVD.† Some data files are provided in ASCII and so you can view them with your browser or other software such as word processors or spreadsheets.
All documentation is provided either as ASCII files, browser pages (html code) or "pdf" files (readable with the free software, Acrobat Reader, see Software pages for details of how to get Acrobat Reader).† You can access the documentation by using your browser to follow the links though each data stream.
Where can I find updated versions of my internet browser?
You may find that if you are using an older version of an internet browser, some of the pages on the DVDs do not load completely.† The Software pages on this Disk provide information on websites where you can obtain updated versions of browsers.
How do I visualise or plot the data?
There are several different ways that you can do this.† The first time user guide for netCDF will tell you how to install on your computer the free Java-based software to read and do simple plots with netCDF files (ncBrowse).† That software will also allow you to export data to ASCII files should you wish to do so.† The Primer will also tell you how to read netCDF files in commercial scientific software or programming languages that you may already be familiar with.†
Alternatively you could make use of the eWOCE facility on Disk 2.† The electronic atlas of WOCE data comes with free software that you can either run from the DVDs or install on your personal computer, called Ocean Data View (ODV). The ODV software will allow you to select data files based on a variety of criteria (location, time etc) and plot them as vertical sections, or profiles, or property-property plots etc.†
Are these data online?
At the time of publishing these DVDs the WOCE Global Data may be available on the internet via various DODS servers (Distributed Ocean Data Servers).† See http://www.unidata.ucar.edu/packages/dods/ for more about DODS which is a system for making data available on the internet. Please be aware that we cannot guarantee that these websites will be active when you attempt to reach them.†
Following the production of the DVDs, Updates and Amendments to the contents will be posted on-line.
What format are the data in?
The data are in a binary format called netCDF that is "self-describing".† This means that any software designed to read netCDF files will recognise all the fields (variables) and units without you needing to have a separate format description.†
Why are the files in netCDF?
The fact that wide variety of WOCE data are in the same kind of data file means that you only need a single piece of software to read them all.† For earlier versions of WOCE data you needed to know the structure of the files and needed a different piece of software or code to read each kind of data stream. In some data streams you even needed different code to read individual files!† This problem has been removed with the use of netCDF.†
What is the easiest way to use netCDF?
You will need to install some software on your computer.† The most basic application (ncBrowse) is Java-based and free, and will allow you to plot the data, view the header information and export to ASCII if you wish to do so (as will ncdump). Otherwise you can read netCDF files with commercial scientific software or programming languages that you are already familiar with. The first time user guide for netCDF (the netCDF Primer, will tell you how to install these applications on your computer.
Is there a first time user guide to netCDF?
Yes, the first time user guide for netCDF (the netCDF Primer) can be found on the Help pages of this Disk.† It will tell you more about netCDF and how to install some necessary software on your computer.
Do the netCDF files conform to any recognised standards?
Yes, the WOCE netCDF files conform to the international standards set by COARDS (Co-operative Ocean/Atmosphere Research Data Service), a USA-based co-operative for the sharing and distribution of global atmospheric and oceanographic research data sets. This means that the variables names associated with the data, the attributes of the data and the time convention follow a common standard for all the different data types within the WOCE Global Data resource and also are common to other data sets that are used by the oceanographic and meteorology communities.† More details about the COARDS and WOCE conventions can be found on the Help pages on the Disk.
Are there ASCII versions of the data files?
Whereas all data are available as netCDF files, only some data streams have ASCII versions. The reason for including ASCII files is to satisfy the requirements of users who have been using them throughout WOCE.† The data streams that contain ASCII files are Bathymetry, Hydrography, Subsurface Floats (not profiling floats), Current Meters, Shipboard ADCP (Acoustic Doppler Current Profilers), Sea Level (Fast Delivery and Delayed Mode), Surface Fluxes, and Sea Surface Salinity.
Why are there zipped files and how do I deal with them?
In some cases files have been "zipped" (a form of compression) to make them a manageable size on the disks; for example the surface drifter data.† In other cases a number of data files have been zipped together as a convenient unit; for example, all float profiles from a single project.† The Software pages on this disk provide more information on the software you need to "unzip" those files.
Where is the long-term archive for WOCE data?
The WOCE data resource, including data files, products and documentation are archived at the US National Oceanographic Data Center (NODC), www.nodc.noaa.gov. Updates and amendments to the contents of the DVDs will be posted online at NODC.