Argo world 

Frequently Asked Questions about Argo Data

Characteristics of the Argo dataset

History of sensor problems in Argo dataset

The Argo dataset over time

Argo data formats

How to access Argo data

What is the difference between an "R" and a "D" profile file?

R files contain data that have only passed automated simple QC tests in real time and so may contain temperature, pressure and/or salinity errors. Most of these errors are the result of sensor drifts. D files have passed expert QC inspection and have had sensor drifts removed. They also have statistical uncertainty assigned to each observation based on both the sensor accuracy and the correction accuracy. If your application requires very high accuracy, use the ADJUSTED fields in the D-files and read and inspect their assigned errors and qc flags.

In particular, if you are doing scientific work sensitive to small pressure biases (e.g. calculations of global ocean heat content or mixed layer depth) Argo recommends the following guidelines:

  1. Users utilise the quality flags in the Argo data files and data labeled with QC = 1
  2. Only use delayed-mode data (D files)
  3. Only use ADJUSTED data variables
  4. PRES_ADJUSTED_ERROR should be checked and where values are greater than 20db, these data should be rejected

If your work is not sensitive to small pressure biases, it is probably acceptable to use "R" files. "R" files should be free from gross errors in position, temperature and pressure. Additionally, if there is a known offset in salinity, this is applied and appears in the PSAL_ADJUSTED variable.

How accurate is the Argo data?

The temperatures in the Argo profiles are accurate to ± 0.002°C and pressures are accurate to ± 2.4dbar. For salinity,there are two answers. The data delivered in real time are sometimes affected by sensor drift. For many floats this drift is small, and the uncorrected salinities are accurate to ± .01 psu. At a later stage, salinities are corrected by expert examination, comparing older floats with newly deployed instruments and with ship-based data. Corrections are made both for identified sensor drift and for a thermal lag error, which can result when the float ascends through a region of strong temperature gradients.

Following this delayed-mode correction, salinity errors are usually reduced further and in most cases the data become good enough to detect subtle ocean change. The estimated accuracy of the delayed mode quality controlled salinity can be found in the PSAL_ADJUSTED_ERROR fields in the D profile files. If the salinity is found to be questionable even after delayed mode adjustment, the error and the qc flag are adjusted to higher than usual to make users aware of this. Therefore, users should use the *_ADJUSTED_ERROR and *_ADJUSTED_QC fields in the profile files to filter the data set to remove less accurate measurements.

This goes for all the parameters measured. While the temperature and pressure sensors are highly accurate, they may still have errors, leading to higher adjusted error fields and qc flags.

In general, data that are considered bad and unadjustable are marked with a qc flag of '3' or '4'. These bad data should not be used in any scientific applications.

What floats have additional sensors like oxygen and how do I get this data?

There is now an argo_merge-profile_index.txt list available on the Argo GDAC ftp which lists all the merged profile file names, date, latitude, longitude, ocean, profiler type, institution, ocean state parameters such as TEMP, PRES, DOXY, etc., and the date of file update. This can be searched, just like the simple argo_profile_index.txt list, for floats in the region of interest with the desired ocean state parameters. Refer to Reference Table 3: Parameter code table in the Argo User's Manual for the name of the different parameters to search for.

To find the intermediate parameters, like TEMP_DOXY, etc, the argo_bio-profile_index.txt on the Argo GDAC ftp must be searched. The same information is included except that the intermediate parameters are listed instead.

Use the Argo Information Centre website to search for floats with additional sensors. Look under the "Monitoring" and then "Floats" tabs to search the float database. Use the "Equipment[s]" tab to indicate which additional sensor or quality you are looking for.

Alternately, you could search the Argo Data Management Data Selection Tool for Argo biogeochemical data.

Note that not all 'additional sensor' data in Argo have undergone quality control and thus may require the user to do this. While Argo distributes these data, they are not part of Argo's current mission.

In V3.1 profile files, oxygen data will reside in the B-Argo profile files and the M-Argo profile files. The B-Argo profile files will contain all parameters a float measures expect temperature, salinity and conductivity. This includes DOXY plus intermediate parameters like TEMP_DOXY, BPHASE_DOXY, etc. The M-Argo profile files will contain all ocean state parameters, so will contain DOXY plus TEMP, PRES, and PSAL. A link to several draft documents explaining these divisions of data can be found here.

In V2 profile files, oxygen data is stored as <PARAM> or <PARAM>2 depending on whether there is more than one oxygen measurement taken each profile.

In V3.0 and higher files, oxygen data resides in the N_PROF =1 dimension if taken using the same vertical sampling scheme as the CTD and in the N_PROF = 2 dimension if taken using a different vertical sampling scheme from the CTD. So, users must search all N_PROF dimensions in the V3 and higher profile files to ensure they find all the oxygen data. This is explained in both the current documentation and the draft documentation on the ADMT website.

There will be a mix of V2 and V3 files as well as core-, B-, and M-Argo files on the GDACs for some time.

Can a float have both an "R" and a "D" trajectory file? Which should I use?

Yes, a float can have both an "R" and a "D" trajectory file with the trajectory 3.0 file format and higher. If both types of files exist, that means that only part of the float's trajectory has been delayed mode quality controlled. A user will have to look in the "D" trajectory file for the delayed mode quality controlled cycles and then in the "R" trajectory file for the additional cycles that have not yet been looked at in delayed mode. This means that users may need to look in two trajectory files to get all of a float's trajectory information.

For example, a float might have its first 35 cycles delayed mode quality controlled and that information is contained in the "D" file. To get information for the next 20 cycles, one must open the "R" file and look for cycles after the first 35 that have been quality controlled.

As with profile files, if a "D" file is available, that data should be used instead of the "R" data since it has been quality controlled by an expert. If no "D" data is available, "R" data can still be used with the knowledge that only a few of the real time qc tests apply to the trajectory files.

Two-way communication and the Argo dataset

The majority of floats deployed in 2017 use the two-way communication system Iridium. With two-way communication, floats will be on the surface for a much shorter amount of time (~30 minutes to 2 hours instead of 8 to 24 hours) and their position will usually be fixed by GPS. Sometimes GPS fixes are not available and other, lower quality fixes can sometimes be used.

Additionally,there is the possibility for the floats to send back a much larger volume of data. Therefore, profiles from Argo floats using two-way communications will likely include many more CTD measurements; the frequency of measurements might increase to every couple of decibars in some areas and parts of the profile. The other files may also include more data.

Finally, float owners may choose to send a signal to their float to change its mission due to the status of the float, an impending event like a tropical cyclone, etc. These changes in mission are recorded in the CONFIG_XXXX variables in the Metadata file.

Do all Argo floats vertically sample pressure, temperature and salinity the same way?

There are mainly two types of CTDs used on Argo floats - one that spot samples and one that continuously samples. The spot sampled CTDs return one spot sample per bin while the continuously sampled CTDs return an average sample per bin. These two methods of sampling can influence heat content calculations and so the new V3 profile format includes a variable that describes the vertical sampling method. It is called "VERTICAL_SAMPLING_SCHEME" and is described in Reference Table 16 in the USer's Manual on the ADMT Documentation page.

How accurate is Deep Argo data?

As part of pilot deployments, Argo profiles reaching below 2000dbar will start appearing in the Argo data system.

The accuracy of the data below 2000dbar is not yet well understood and so Argo is currently labelling these data with lower quality flags (2 and 3) in real time.

We warn users to treat these data with care and recognize that we cannot guarantee they have the same accuracy as Argo data collected above 2000dbar. As more is learned about sensor performance below 2000dbar, the flags and an accuracy assessment will be updated.

Such floats can be easily identified from metadata files, using PLATFORM_FAMILY='FLOAT_DEEP' and PLATFORM_TYPE ( Please note that this reference table is frequently updated to include new sensor and float models. You can find the latest version at: ). This is also explained in the latest version of the User's Manual found in the Documents section of the ADMT website.

Alternatly, WMO IDs of deep Argo prototypes can be found in this status file maintained at the AIC containing information on all Argo floats. In the column labelled "PTF_MODEL", deep Argo floats are described with "float_D".

For example, one can find deep Argo floats called "SOLO_D" or "ARVOR_D"..

Salinity error in some SBE CTD cells

Due to a manufacturing problem that occurred a few years ago, a larger than normal number of SeaBird Scientific CTD cells (Serial Numbers 6000-7100) used in Argo developed a high salinity bias within two years of deployment. Many of these CTDs are still active in Argo, and as result, a higher portion of Argo real time data than normal are subject to salinity errors outside of the Argo 0.01 accuracy target.

Our best estimate is that, in August 2018, about 25% of real time profiles might be subject to this bias. The Argo national Data Assembly Centers are working on identifying the afflicted cells and grey-listing their salinity channels. While this process is occurring we strongly advise that for real time applications sensitive to these salinity errors, users ensure they check the grey list, read and apply all the QC flags, use the adjusted fields and carefully check their results. For climate analyses, we strongly recommend only using delayed-mode data.

The Argo Program is working as fast as possible to identify and grey list these cells, and correct (where possible) their data. We are also working closely with the manufacturer (SeaBird Scientific) to understand the source of the drift in order to more confidently correct the errors and prevent a re-occurance of this problem.

List of SBE CTDs by serial number in excel and txt format.

SBE CTD pressure calibration error

In September 2015, a firmware bug was introduced in the development of the SBE41plus sensor that extended to the SBE 41N and the SBE 61. The bug is confined to one operating command, "tpr", which causes the CTD to output raw pressure sensor analog to digital counts.

The "tpr" command is used in pressure sensor calibration. The result of the bug is that pressure calibration coefficients are calculated with raw pressur data that is in error. The magnitude and sign of the error depends on each individual analog to digital converter. Most analog to digital converters produce little or no error and are within the pressure accuracy specification.

The table below lists starting and ending CTD serial numbers that are affected by the pressure calibration error. Note that SBE 41plus and SBE 41N share the serial number sequence.

Starting Serial Number Ending Serial Number
SBE 41plus / 41N 41-7504 11055
SBE 61 61-5578 5645

Float original equipment manufacturers (OEM) and Navis floats use the 41plus, Biogeochemical and deep pH Navis floats use the 41N, and Deep Argo floats use the SBE 61.

A work around implemented in Sea Bird's pressure calibration process was put in place on 18 June 2018. Pressure calibrations done after that date are correct even if they are within the serial number range shown above.

Impact to the Argo fleet
An estimation of the number of effected CTDs can be made from Dana Swift's SBE 41 acceptance testing data. These data are gathered by placing the CTD in a temperature controlled environment and measuring the CTD pressure accuracy at full range (2000 decibars). The table below shows the percentage of CTDs that are out of specification at cold temperatures and full range for the SBE 41 and SBE 41plus CTDs.

SBE 41 SBE 41plus
Average error in decibars -1.52 -0.48
Standard deviation 1.13 1.40
Total tested 391 210
Total out of spec 35 12
Percent out of spec 9% 6%

For more information on this error, see the error notice from Sea Bird.

APEX truncated negative pressure drifts

APEX floats do not self-correct their pressure measurements, and so the raw pressures returned by APEX floats can contain errors as a result of pressure drifts. Historically, APEX floats have used pressure sensors from Paine, Amatek and Druck, all of which have exhibited pressure drifts of various magnitudes. Therefore APEX pressures are corrected to surface pressure offsets (SP) in real-time by the DACs and in delayed mode by float experts.

Unfortunately, it is not always possible to correct the raw pressures from APEX floats. Some APEX controller boards, APF5-8, restrict SP to values greater than zero with negative SP values truncated to zero. Thus, if a pressure sensor develops a negative pressure drift on floats with an APF8 or earlier series controller, the reported SP values are always zero. Profiles from these periods are labeled as having "Truncating Negative Pressure Drifts" or TNPDs and are not correctable. Given the fast changing nature of Argo data, it is best to identify TNDP affected profiles by looking for the PRES_ADJUSTED_ERROR = 20 dbar.

Before the data set was corrected and these floats identified, the effect of the APEX pressure biases was to overestimate the temperature in the oceans and to create errors of about 10% of the magnitude of salinity differences between Argo and WOA01 datasets. The largest temperature errors occurred in the upper 200 m of the water column (due to the steep thermocline gradient), prior to 2005. This, in turn, incorrectly implied a smaller global mean upper-ocean warming and thermosteric sea level rise from 2003 to 2008. (Barker et al, 2011).

Argo now audits the treatment of pressure biases in the global data set. Most data are now corrected. TNPD affected profiles can be identified in profile files through the character string "TNPD" in the SCIENTIFIC_CALIB_COMMENT field for PRES. TNPD data are labeled with *_ADJUSTED_QC = '2'. The more severe ones have PRES_ADJUSTED_ERROR = 20db.

The following two papers describe in more detail the pressure biases for APEX floats:

Barker, P. M., J. R. Dunn, C. M. Domingues, and S. E. Wijffels, 2011: Pressure Sensor Drifts in Argo and Their Impacts. Journal of Atmospheric and Oceanic Technology, 28, 1036-1049,

J.P. Abraham, M. Baringer, N.L. Bindoff, T. Boyer, L.J. Cheng, J.A. Church, J.L. Conroy, C.M. Domingues, J.T. Fasullo, J. Gilson, G. Goni, S.A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G.C. Johnson, S. Kizu, J.M. Lyman, A. M. Macdonald, W.J. Minkowycz, S.E. Moffitt, M.D. Palmer, A.R. Piola, F. Reseghetti, K. Schuckmann,K.E. Trenberth, I. Velicogna, J.K. Willis, A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change, Reviews of Geophysics, (accepted).

SOLO FSI CTD pressure offset errors

In early 2007, it was discovered that Argo profiles from SOLO floats with FSI CTD (Argo Program WHOI) may have incorrect pressure values. The problem did not affect any other combination of instrument and sensor. In GTS TESAC messages, potentially affected instruments can be identified by instrument type 852 (SOLO FSI, see WMO Code Table 1770).

Some profiles can be corrected automatically and some need additional study. The automatic fix for these profiles was instituted on 10 October, 2007. For profiles need additional attention, the float will stay on the greylist until the profiles have been fixed.

While studying the pressure offset errors, a related problem was discovered in a group of WHOI/SBE profiles. For the affected WHOI/SBE instruments, all profiles have been corrected and are available on the GDACS as of 14 September 2007.

To learn more details about the pressure problems, click here and to learn which floats have been fixed, click here

Druck pressure sensor micro-leak problem

In early 2009, it was discovered that a large number of Druck pressure sensors were experiencing oil micro-leak problems. See for more details. Druck pressure sensors were in most of the active Argo floats, making all float models potentially affected. The negative pressure drift resulting from this oil micro-leak can happen either gradually or quickly and the size of the drift can also vary, but goes up to tens of dbars.

To fix this problem, the manufacturing process of the Druck pressure sensor was modified and additional tests are done on the sensors. Sea-Bird has also begun using a new pressure sensor made by Kistler. Floats with fixed Druck sensors or Kistler sensors were being deployed by late 2009.

The three major types of Argo floats (APEX, SOLO, and PROVOR/ARVOR) treat pressure sensor drifts differently. APEX floats report the raw pressure sensor output at the end of their surface satellite transmission without any self correction. This means that raw APEX pressure data must be corrected in real-time by the DACs and in delayed-mode by float experts. Please refer to the section on "APEX truncated negative pressure drifts" for more information.

SOLO and PROVOR/ARVOR Argo float models are programmed to auto-correct for pressure drift on board the float using the measured surface pressure offset. For these self-correcting floats, only when the offset correction is insufficient do the data need to be flagged as questionable.

The following two papers describe in more detail the pressure biases within the Argo dataset:

Barker, P. M., J. R. Dunn, C. M. Domingues, and S. E. Wijffels, 2011: Pressure Sensor Drifts in Argo and Their Impacts. Journal of Atmospheric and Oceanic Technology, 28, 1036-1049,

J.P. Abraham, M. Baringer, N.L. Bindoff, T. Boyer, L.J. Cheng, J.A. Church, J.L. Conroy, C.M. Domingues, J.T. Fasullo, J. Gilson, G. Goni, S.A. Good, J. M. Gorman, V. Gouretski, M. Ishii, G.C. Johnson, S. Kizu, J.M. Lyman, A. M. Macdonald, W.J. Minkowycz, S.E. Moffitt, M.D. Palmer, A.R. Piola, F. Reseghetti, K. Schuckmann,K.E. Trenberth, I. Velicogna, J.K. Willis, A review of global ocean temperature observations: Implications for ocean heat content estimates and climate change, Reviews of Geophysics, (accepted).

Kistler pressure sensor problem

In June 2016, a defect mode was discovered in Kistler pressure sensors. Click here for more details directly from Sea-Bird. The problem consists of a sudden jump shift in the pressure span (the calibration slope of pressure). The root-cause of the defect, found by Kistler, is an electrical component in the pressure bridge circuit that becomes disconnected from the circuit board. The pressure span shift results in a higher reported pressure than actual pressure. For example, a defective sensor reporting 1200 dbars at 1000 dbars depth, reports +2 dbars at the surface.

The effect of pressure error is that all variables will plot incorrectly in pressure space, and calculations involving pressure will be wrong. CTD temperature is correct, but computed salinity values will be systamtically low of correct.

Sea-Bird feels that they have identified most of the sensors during routine manufacturing processes and have thus prevented most of them from being deployed on floats. Argo float providers are being asked to review their data from CTDs with Kistler pressure sensors to identify any other possible problems.

I have downloaded a "D" profile file. Will I ever need to download this file again?

The Argo dataset is always changing and a "D" profile file or trajectory file may be modified after it is first created. If you are maintaining your own mirror of the Argo GDAC, it is important to keep this up to date. If you are only using a selection of Argo profiles, it is still important to regularly check the GDAC to see if the file has been updated.

Are there archives of the Argo dataset?

US NCEI maintains the Global Argo Data Repository (GADR) for Argo data and is responsible for managing updates to Argo data from reanalysis. Even with this archive, it is strongly recommended that users obtain Argo data from the Argo GDACs as they are updated and improved daily.

Does the Argo dataset have a DOI?

Yes, Argo is now generating DOIs based on monthly snapshots of data at the GDACs. There are also DOIs for the Argo User's manual and the Argo GDACs. To find all the Argo DOIs, click here.

Authors are encouraged to use the Argo DOIs as well as the acknowledgment stated here:

What is the status of the new V3 & higher data format roll-out?

Currently, most DACs are producing a majority of all file types in V3.1.

What is new in the V3 & higher profile file?

The major change in the format of the V3 & higher profile files is the ability to accommodate multiple profiles from a sincle cycle. As floats begin performing increasingly complex missions, it is necessary to be able to differentiate the vertical sampling scheme for the various parameters. A detailed explanation is available here. A brief description follows.

Some specialty floats collect additional profiles per cycle which contain parameters measured at different pressure levels from the CTD and might be at different locations and times than the core profile. Examples of specialty profiles include high resolution near-surface observations, bouncing profiles, etc.

The number of profiles is indicated by the N_PROF dimension where the N_PROF = 1 profile must have the Primary sampling profile. Other profiles with different vertical sampling schemes will have N_PROF > 1. A new variable, VERTICAL_SAMPLING_SCHEME, differentiates the various vertical sampling schemes which can change between cycles to accommodate floats with two-way communication. Reference table 16 gives the formats of the different string codes that may appear in the variable. The number of pressure levels is indicated by the N_LEVELS dimension.

More detailed information on the changes can be found in the Argo User's Manual found at the Argo Data Management website.

The V3.1 profile files will be split into core, B- and M-Argo profile files. The core- and M-Argo profile files contain the CTD sensor parameters (pressure, temperature, salinity, conductivity) that are measured with the same vertical sampling scheme and at the same location and time in the N_PROF = 1 dimension. Additional parameters from other sensors are stored in a B-Argo profile file. A float that performs only CTD measurements will not have B-Argo files. The link between the core- and B-Argo files is PRES.

These files with the additional parameters can be identified by the "B" that precedes the WMO ID in the file name. In addition, the GDACs are planning to implement a file merging procedure that will add the derived parameters from the B-file to the core data so you can acquire the full set of data from a float without downloading the raw parameters from the B-files. These will be identified by 'M' so it will be necessary to consider carefully what files to download.

What is new in the V3.1 traj file?

The new V3.1 traj files have been modified to include more information about the events during a cycle and the times associated with these events. A detailed explanation is available here. A brief description follows.

One major difference is the new MEASUREMENT_CODE variable that indicates what type of measurement is occurring and the codes can vary significantly from one float type to the next. The codes are all explained in Reference table 15 of the User's Manual.

Another change is the addition of the JULD_ADJUSTED variable which contains the best estimate of the float timing available for that float. This may or may not be filled in real time.

Some additional cycle timing variables are included in the N_CYCLE array to more completely describe the timing of events in each cycle.

Finally, there will be a two-file system for trajectory files; there will be Real Time (R) and Delayed Mode (D) trajectory files. R files will contain only real time data and will be created by DACs. D files will contain all data, ie both real time and delayed mode data, and will be created by the scientist responsible for the float.

It is possible that a float may have both an R and a D traj file and a user must look at both files to get the entire trajectory information for that float.

In V3.1 traj files, it is possible to store changing resolutions for the various <PARAM> variables. If the resolution does not change, look for the "resolution" attribute for the variable (usually PRES). If the resolution does change throughout the cycle, no "resolution" attribute exists and one must look at the "comment_on_resolution" attribute to find the resolution.

What is new in the V3 & higher meta file?

The V3.0 meta files contain two new variables to help document a float's mission and possible change in mission during the float's lifetime. A detailed description is available here. A brief description follows.

The new variables are CONFIG_MISSION_NUMBER and CONFIG_PARAMETER_VALUE. Users can determine the mission number a float is performing for that cycle using the CONFIG_MISSION_NUMBER variable in the new V3.0 traj and profile files.

Many floats perform only one mission their entire lifetime and so will always have a mission number of 1. However, with the addition of two-way communication and more sensors, some floats are changing their mission during their lifetime or have more than one mission from the beginning. Reference table 16 in the User's Manual explains the configuration parameter names.

The V3.1 meta files have an N_SENSOR dimension indicating the number of sensors a float carries as well as an N_LAUNCH_CONFIG_PARAM dimension indicating the number of pre-deployment or launch configuration parameters. There is a new set of LAUNCH_CONFIG_XXXX variables that contain all the pre-deployment or launch configurations.

There is also a new series of variables related to float parameters which help to identify which sensor is measuring which parameter.

What is a core-Argo file? What is a B-file? What is an M-file?

There will now be core-Argo, B-Argo and M-Argo profile and trajectory files. The core-Argo profile and trajectory files will look very similar to files previously on the GDACs. In fact, if the float only has a CTD, there is no difference between the old file and the new core-Argo profile and trajectory file. The names of the files remain the same and the parameters within them remain the same. The parameters included in a core-Argo file will be pressure, temperature, salinity, and perhaps, conductivity.

The B-files will include any Argo parameter except temperature, salinity and, if applicable, conductivity. They will also include any intermediate parameters that are necessary to calculating ocean state parameters.

The M-files, where "M" means merged, will contain all ocean state variables that a float measures. Examples of additional ocean state parameters that might be present in an M- file are DOXY, CHLA, etc. This file will be a combination of the core parameters and any other ocean state parameters found in the B-file.

For more information on these files, including their naming conventions and the list of parameters, visit the "Separation of Core-Argo and B-Argo data files" section of the draft document page on the Argo Data Management page at: draft documents.

The split into core-, B- and M-Argo files starts with V3.1. Earlier format versions will contain biogeochemical data in the profile and trajectory files.

What cycle timing information should Argo floats send back?

Each Argo float cycle is composed of programmed events. Depending on float type, some of these events can be dated and sent back by the float to aid in the calculation of velocities. The Argo Program has highlighted several cycle timing variables that it would prefer that floats send back timing information. This cycle timing document explains the variables and how they fit into the trajectory file.

How do I search for data in a specific time and location?

The answer to this question depends on many things such as much Argo data you are looking for, how frequently you anticipate looking at the data, how you want to access the data and what sort of a computer programmer you are.

As a way to get started, both GDACs offer ways to search for data in a specific time and location and then download that data. The US GDAC has a GUI data browser that allows one to look for profile or trajectory files using date, location, DAC, real or delayed mode data and float ID as search criteria. The link is: It is possible to download the NetCDF files right away as a tar file.

The Coriolis GDAC also offers a data selection page that allows one to search for Argo profile or trajectory data using date, location, real or delayed mode data, float ID and data type as search criteria. The link is: You can request to have the files emailed to you in NetCDF or ASCII.

Both of the previous methods work well if you are not interested in maintaining your own copy of the Argo dataset on your computer. If you do want to keep your own copy, index files exist which make searching with various criteria easy. There is an index file for profile files, trajectory files and meta files. Each index file has one line for each Argo file that exists along with metadata about time, location, DAC, etc. The index files can be found on the FTP sites at both GDACs: Coriolis and US GODAE.

Another alternative is to use the Google Earth layer developed by the Argo Technical Coordinator (argo.kml). This makes it possible to see the latest positions of all the active and inactive Argo floats. One can also look at the float's trajectory. This is a great way to search for floats in a small area.

Are there gridded or other data sets based on Argo available?

Yes, there are various gridded fields and other data sets available using only Argo data or Argo data plus others. Most of these files are NetCDF files and all are freely available for download, although some require an account. There are gridded temperature, salinity and velocity files as well as other velocity products and Standard Depth Level products. The Argo Program does not create these files, but maintains a database of the known products. See the Data Products page for more information.

Is there an easy way to view Argo data? What is the Marine Argo Atlas?

Yes, the Global Marine Argo Atlas takes the gridded Argo-only NetCDF file produced at Scripps Institution of Oceanography ( and makes a GUI that allows users to plot of various maps of Argo data. There are map views, sections, line plots, time series and a few simple products. The data start from 2004 when the Argo array first reached a global nature and continue to the previous month. This atlas works particularly well for those not interested in learning how to work with NetCDF files. The interested user can also work outside the GUI, using line commands, to create the exact plot they are interested in.

There are a few other viewing options available on the Data viewers page.

Are there any resources for using Argo data in the classroom?

Yes, there are ways for students to access Argo data in the classroom. There is an education page with curriculum, websites, data viewers and access to Google Earth layers. The data viewer, also called the Marine Atlas, relies on gridded Argo data to produce plots of temperature, salinity, density, and velocity on global or regional scales. It is also possible to look at profiles at specific locations.

The EuroArgo Education page offers great explanations of how to interpret plots of data as well as how to look at the data in Google Earth. There is an Argo layer for Google Earth that displays individual floats, trajectories, float stories and more.

Is there a way to display data in Google Earth?

Yes, see the Argo layer for Google Earth page for information on how to display individual floats, trajectories, float stories and more.

Does Argo have an API?

Yes, the North Atlantic Regional Centre (NA-ARC) has developed an Application Programming Interface, or API, for the North Atlantic region. It is possible to search for floats by region, time, QC flag, data mode, etc. The complete documentation with examples and a quick start guide to use the API (from your browser but also scripts in matlab or python) is available here:!DocAPI. The NA-ARC web API base url is: API services are provided by adding parameters to the base url.

What if I have questions about Argo or the data?

If you have general questions about Argo, please send them to
If you have more technical questions about the data, please look at the support website or e-mail the support desk (