Estimation of secondary phytoplankton pigments from satellite observations using self‐organizing maps (SOMs)

Roy El Hourany (1, 2) , Marie Abboud‐abi Saab (2) , Ghaleb Faour (2) , Olivier Aumont (3) , Michel Crépon (1) , Sylvie Thiria (1)

1 VARCLIM - Océan et variabilité du climat
2 National Center For Remote Sensing [CNRS-L]
3 NEMO R&D - Nucleus for European Modeling of the Ocean

This study presents a method for estimating secondary phytoplankton pigments from satellite ocean color observations. We first compiled a large training data set composed of 12,000 samples; each sample is composed of 10 in situ phytoplankton high-performance liquid chromatography (HPLC)-measured pigment concentrations, GlobColour products of chlorophyll-a concentration, and remote sensing reflectance (Rrs($\lambda$)) data at different wavelengths, in addition to advanced very high resolution radiometer sea surface temperature measurements. The resulting data set regroups a large variety of encountered situations between 1997 and 2014. The nonlinear relationship between the in situ and satellite components was identified using a self-organizing map, which is a neural network classifier. As a major result, the self-organizing map enabled reliable estimations of the concentration of chlorophyll-a and of nine different pigments from satellite observations. A cross-validation procedure showed that the estimations were robust for all pigments (R$^2$>0.75 and an average root-mean-square error=0.016mg/m$^3$). A consistent association of several phytoplankton pigments indicating phytoplankton group specific dynamic was shown at a global scale. We also showed the uncertainties for the estimation of each pigment.

Domaines: Géophysique [physics.geo-ph]; Planète et Univers [physics]

Roy El Hourany, Marie Abboud‐abi Saab, Ghaleb Faour, Olivier Aumont, Michel Crépon, et al.. Estimation of secondary phytoplankton pigments from satellite observations using self‐organizing maps (SOMs). Journal of Geophysical Research. Oceans, 2019, 124 (2), pp.1357-1378. ⟨10.1029/2018JC014450⟩. ⟨hal-02193255⟩