Handbook of best practices

Figure 5.2.1 a: Oxygen measurements through optodes 4330 mounted on Argo floats. The line colors represent
the different floats deployed over 3 days in pool for testing. The dots represent the Winkler in situ sampling. The
mean difference between optodes on floats and Winkler values ranged around 5-12 µmol/L.
Once the optode measurements have been done, it is recommended to proceed to some
corrections. Two methods are usually proposed:
• adjusting the calibration coefficients by using a polynomial fitting model (in situ
Winkler or WOA climatology or pO2 in air are used as oxygen reference value)
• simple linear method to estimate the offset and gain (slope) of oxygen data
(Takeshita et al., 2013).
DOXY_adj [µmol/L] = offset + gain x DOXY [µmol/L]
The second method proposed here is easier and any modifications of calibration coefficients
are necessary. However, a large amount of in situ or climatology data is required to
guarantee the robustness of the optode correction.
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