On January 9, 2024, (http://doi.org/10.17882/42182#107470), in the Argo data stream, very few Chlorophyll-A (Chla) profiles are available in Delayed Mode (DM). For SOCA2024 (Sauzede et al., 2016) development, we have applied a specific post-processing that acts similarly to a DM adjustment to improve Chla accuracy, but unlike DM data, data produced are not fully scrutinized. This post-processing procedure aims to apply three main corrections:

1) the median of the minima for dark correction;

2) the Non-Photochemical Quenching (NPQ) correction from Terrats et al. (2020), adapted from Xing et al. (2018), based on both Photosynthetically Available Radiation (PAR) and b_bp measurements;

3) the physiological correction factor of fluorescence into Chla determined from the method of Xing et al. (2011), based on the vertical profile of Ed(490), the downwelling irradiance at 490 nm.

We applied this procedure to all the BGC-Argo fleet measuring fluorescence, including floats that are non-equipped with a radiometer. For those floats, radiometric parameters [(PAR and Ed(490)] were modelled thanks to the SOCA-light method (Renosh et al., 2023). SOCA-light needs a satellite ocean colour matchup with Argo profile to derive PAR and Ed(490) profiles. The availability of an ocean colour matchup is not an issue for the physiological correction factor as the median of all the slopes computed over the whole float lifetime is used allowing every float to have a slope estimation. However, for the NPQ correction that is applied on a profile-by-profile basis, when the ocean colour matchup is not available, the SOCA-light-derived climatological PAR profile was used to evaluate the depth till the NPQ should be corrected. This NPQ method correction is more accurate than the Xing et al. (2012) method used currently in A-mode that only takes into account an estimation of the mixed layer depth. All the QC flags were then processed in accordance with BGC-Argo standard protocols (Schmechtig et al., 2023).

Schematic representation of the post-processing of Chla data used for SOCA2024 training. The dashed rectangle corresponds to the correction applied using the median of data for the entire lifetime of float estimations. For instance, dark values are corrected by applying the median of all dark values computed across all profiles of the float's lifetime. The satellite indicates where a direct ocean colour matchup is required to obtain a value.