Retrieval of the Particle Size Distribution Using Coated Spheres and Two Particle Populations Mie Modeling
Abstract
The particle size distribution (PSD) of particles (including phytoplankton cells) suspended in near surface ocean waters is a key property affecting marine ecosystem structure and function, as well as ocean optics. Phytoplankton size classes (PSCs) are closely related to phytoplankton functional types. The size structure of the phytoplankton community affects the biological pump and is thus important for elucidating ocean ecosystem role in the carbon cycle. The KSM09 ocean color algorithm (Kostadinov et al., 2009) uses homogeneous sphere Mie modeling to retrieve the parameters of a power-law PSD from the spectral particulate backscattering coefficient (bbp). The PSD can subsequently be used to retrieve carbon-based PSCs (Kostadinov et al., 2016). Here, we present a significant update to KSM09, in which phytoplankton cells and non-algal particles (NAP) are modeled as two distinct particle populations. Phytoplankton are modeled as coated spheres, based on the Equivalent Algal Populations (EAP) framework (e.g. Robertson-Lain and Bernard, 2018). NAP are modeled as homogeneous spheres. Phytoplankton and NAP PSDs are assumed to have a common PSD slope. Akin to KSM09, a forward model is built in which the simulated spectral shape and magnitude of bbp is related to the underlying PSD parameters, which are retrieved using spectral angle mapping. Modeled fraction of bbp due to NAP is compared against recent global satellite retrievals (Bellacicco et al., 2018). PSD retrievals are demonstrated using the Loisel et al. (2018) algorithm to estimate bbp from ocean color data. Monte Carlo simulations are used to assess uncertainty.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMOS0450003K
- Keywords:
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- 4805 Biogeochemical cycles;
- processes;
- and modeling;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL;
- 4817 Food webs;
- structure;
- and dynamics;
- OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL;
- 4264 Ocean optics;
- OCEANOGRAPHY: GENERAL;
- 4273 Physical and biogeochemical interactions;
- OCEANOGRAPHY: GENERAL