Nitrate: Vertical Offset correction between PSAL/CTD and spectra/SUNA missing? #6
Description
In many (all) floats, the nitrate sensor and the CTD are not at the same level, but offset by about 1.5 m. This leads to mismatch issues when 1:1 merging/using measured TEMP/PSAL and measured SUNA data, acquired at the same time but different height (see above), causing spurious spike artifacts in NITRATE at strong TEMP/PSAL gradients, e.g., the base of a mixed layer.
As noted in Processing Bio-Argo nitrate concentration at the DAC Level Version 1.1 March 3rd 2018, section 3.1 Vertical offset, the meta file contains in CONFIG_SunaVerticalPressureOffset_dbar the value of the vertical offset between SUNA and pressure sensor. This should be used to linearly interpolate TEMP (in Eq. 3) and PSAL (in Eq. 4) to the depth of the nitrate sensor, according to the processing manual, prior to proceeding with the TCSS nitrate calculation.
I suppose this should go into nitrateproc.m?