DRAFT Getting started with GO-BGC Data
Everything you need to begin working with the data
GO-BGC data can be used freely, with no restrictions. However, we ask that GO-BGC is properly acknowledged when used in a publication or a product.
Float data can be accessed in various formats through multiple data portals
Research ships deploy floats throughout the world ocean.
Every 10 days floats travel from 2000m to the surface collecting data all the way.
At the suface the float transmits this profile data to GDACs via satellite.
Raw data is available within 24 hours of upload from the float.
GDACs also deliver Real-time Adjusted Data once a float has provided a minimum of 6 profiles. Real-time Adjutsed Data is also available within 24 hours of receiving at the GDAC.
Three times a year all new data goes through a further analysis and correction and is then listed as Delayed-Mode Adjusted Data.
Every 10 days floats travel from 2000m to the surface collecting data all the way.
At the suface the float transmits this profile data to GDACs via satellite.
Three times a year all new data goes through a further analysis and correction and is then listed as Delayed-Mode Adjusted Data.
GDACs also deliver Real-time Adjusted Data once a float has provided a minimum of 6 profiles. Real-time Adjutsed Data is also available within 24 hours of receiving at the GDAC.
Raw data is available within 24 hours of upload from the float.
Utilizing GO-BGC Data
GO-BGC float data are available within 24 hours of receipt of float transimission. To select, download, and visualize GO-BGC data, toolboxes are avialable in MATLAB, Python, and R. These toolboxes access the synthetic profile (s-prof) files directly from the Argo GDAC. Detailed instructions on how to read s-prof files are included in the Github readme files linked below and available through these tutorial videos:
GO-BGC Data Tutorials
Data Access Intro
MATLAB
GitHub Link: MATLAB
Python
GitHub Link: Python
R
GitHub Link: R
Key functionalities of the toolboxes allow you to:
- Download a specific float using its WMO ID number
- Select and download floats that are equipped with desired sensors
- Select and download profiles made within a specific geographic location and time
- Create a variety of plots, including trajectory of float(s), raw and QC’d profile data, and contour plots.
Data Practice
Example 1:
Download float 5904859. Plot float trajectory, and contour plot of only ‘good’ data.
Example 2:
Find floats with nitrate sensors near Ocean Station Papa between 2008 and 2018.
- # of matching profiles: 1810
- # of matching floats: 7
Plot the mean profile and standard deviation for oxygen and nitrate.
Example 3:
Find floats with profiles near Hawaii between 2017 and 2019.
- # of matching profiles: 252
- # of matching floats: 5
Show only the profiles within the region of interest.
Data Adjustment
BGC float data are automatically adjusted to deliver science quality data in near-real time following established protocols that are specific to each parameter. Documentation on how each parameter is adjusted can be found here. Below, you can find videos that summarize the adjustment process, as well as the quality of the resultant data.
O2 Measurements
For adjusting O2 data skip to
29:16
pH Measurements
For adjusting pH data skip to
24:39
Nitrate Measurements
For adjusting nitrate data skip to
19:52
Delayed Mode Quality Control
Please read this methods article by Tanya Maurer, Josh Plant, and Ken Johnson at MBARI to learn more about Delayed Mode Quality Control
Post-deployment quality control (QC) of float-based oxygen, nitrate, and pH data is a crucial step in the processing and dissemination of such data, as in situ chemical sensors remain in early stages of development. In situ calibration of chemical sensors on profiling floats using atmospheric reanalysis and empirical algorithms can bring accuracy to within 3 μmol O2 kg–1, 0.5 μmol NO3– kg–1, and 0.007 pH units..
Routine QC efforts utilizing these methods can be conducted manually through visual inspection of data to assess sensor drifts and offsets, but more automated processes are preferred to support the growing number of BGC floats and reduce subjectivity among delayed-mode operators. The BGC-Argo data center at MBARI has developed the SAGE and SAGE-O2 software tools to facilitate the QC process. The paper by Maurer et al. describes these tools, which are available to the public on Github.