Ocean color algorithm for the retrieval of the particle size distribution and carbon-based phytoplankton size classes using a two-component coated-sphere backscattering model

Abstract. The particle size distribution (PSD) of suspended particles in near-surface seawater is a key property linking biogeochemical and ecosystem characteristics with optical properties that affect ocean color remote sensing. Phytoplankton affects their physiological roles, e.g., the biological carbon pump, which has an important role global cycle thus climate. It to develop capabilities for measurement predictive understanding structure function oceanic ecosystems, including PSD, phytoplankton classes (PSCs), functional types (PFTs). Here, we present satellite algorithm retrieval parameters assumed power-law PSD. forward model considers two distinct populations: non-algal (NAPs). are modeled as coated spheres following Equivalent Algal Populations (EAP) framework, NAPs homogeneous spheres. uses Mie Aden–Kerker scattering computations, spheres, respectively, total particulate spectral backscattering coefficient sum NAP backscattering. PSD achieved via angle mapping (SAM), end-members created by model. used retrieve size-partitioned absolute fractional concentrations (i.e., carbon-based PSCs), well organic (POC), using allometric coefficients. This formulation also allows estimation chlorophyll concentration retrieved percent due vs. phytoplankton. operationally applied merged Ocean Colour Climate Change Initiative (OC-CCI) v5.0 data set. Results initial validation effort presented POC, picophytoplankton situ measurements. Validation results indicate need empirical tuning concentrations; however these comparison other algorithms ambiguous tuning. latter finding illustrates continued high-quality, consistent, large sets carbon, related variables facilitate future improvements.