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Profiling Float and Glider DataContents |
Background
The Argo programme is an international effort to sample the global, offshore, upper ocean on a 10-day time scale. The programme uses profiling floats in this effort and both the deployment of floats and management of the data are co-ordinated internationally. The Argo Data Management Team is responsible for all aspects of handling the data. There is lots of information available about the science programme as well as about the data management component. Through this latter link, you will find references to the Argo Data Management Handbook and a Beginner's Guide. Both of these are good introductions to the Argo programme.
The Euro-Argo programme has developed a web site that also has interesting examples of uses of Argo data. A quick survey of this web site will prove educational and demonstrate uses of such data. Real-time delivery of the data is a requirement for participation in Argo.
There was a Community White Paper on Argo Data Management prepared for the OceanObs'09 meeting. While this repeats some of the information provided in the other documents cited, readers should find this informative.
Finally, there is a host of information available at the Argo Information Centre.
Anyone contemplating buying and deploying a profiling float are advised to consult participants in the Argo programme. They are well informed of all the issues of using profiling floats and their experience will be very helpful.
Step 1: Getting identifiers
Before your profiling floats can report data in real-time they need to be assigned a unique WMO identifier. Each country has been assigned a block of numbers for its use and the country's national focal point can provide identifiers for you (choose “Contacts” from the left hand menu then “Argo National Focal Points” in the pull down list). If your country has never deployed Argo floats before, contact the Argo Technical Co-ordinator.Note that Argo identifiers are never reused; when a float dies, its identifier dies with it. These can be identified on the GTS by numbers preceded by “Q9”.
Getting data ashore via Service Argos
Use of the Service Argos system is one of the ways that data are transmitted from floats to shore. The Section below on “Additional Resources provides a link to the home page of this company.
Step 2: Telecommunications at Service Argos
Service Argos provides two services for profiling float operators. For the first service, they provide telecommunications facilities to relay data from the float to shore. In order to do this, your float must be equipped with an Argos transmitter and you must have an account at Service Argos. Consult Service Argos personnel or speak to the Argo Technical Co-ordinator.
Step 3: Formatting data at Service Argos
The second service offered by Service Argos is to decode the messages coming from your float, apply the standard Argo quality control tests, reformat to TESAC and/or BUFR code forms (see the document “Formats for Rael-time Data Exchange) and insert the data onto the GTS (Global Telecommunications System – see Additional Resources). For details of how to initiate this, speak to a representative from Service Argos or the Argo Technical Co-ordinator. If this system is your choice, once you have made arrangements with Service Argos, you have nothing more to do to get the data distributed.
Step 4: Distributing data through Service Argos
In addition to sending data to the GTS, Service Argos also will transform the data into the standard exchange format for Argo and forward the data to the Global Data Assembly Centers (GDACs), one in the USA and one in France. These centres provide mirror sites where users can find Argo data. The sites are updated every day.
Getting data ashore via Iridium
The Iridium cell phone system is another way to get data ashore. The advantages of this is that there is greater bandwidth for at sea communications (though power requirements are higher). This allows sufficient bandwidth such that all of the profiles collected on a single ascent of a float can be transmitted in a single message to a receiver. These data can then be forwarded to the national processing facility, or to Service Argos, which offers a service as described in Step 3 above.
For more information about how to use Iridium, contact the Argo Technical Coordinator and ask for a contact of someone already using this system.
Getting data ashore via National Systems
Some countries choose to do their own processing of data received from the floats and take care of getting the data to the GTS. Your country may be one of these and so it is important to talk to your Argo National Focal Point (see Step 1). If your country does its own processing, the Argo National Focal Point will put you in touch with the national processing facility.
You can download the data from your floats through contact with either Iridium or Service Argos. After this, it is your responsibility to meet the data distribution requirements on the Argo programme. The Argo Data Management Handbook describes these responsibilities.
Step 5: Quality control.
The Argo programme has published a quality control manual that describes procedures for testing data before they are distributed in real-time. This document also describes how to set quality control indicators in the data format reported to the GDACs. Typically data get to the GDACs within a day or two of the data being distributed on the GTS. The GDAC data format uses netCDF and provides a much richer information content than the GTS data formats.
Additional Resources
GTS: http://www.wmo.int/pages/prog/www/TEM/GTS/index_en.html
JCOMMOPS (for general information on ocean observing programmes): www.jcommops.org/
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Information about this article
Short title: Profiling Float Data
Description: This provides information about exchange of data acquired by profiling floats and gliders.
Expertise level: beginner
Author: bob.keeley
Approval status: approved
Approved by: bob.keeley
Last change: 2012-2-10
Subsection of: Exchanging Ocean Data in Real-time
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