The PACE-MAPP Polarized Ocean Bio-optical Model

The MAPP polarimeter retrieval algorithm, originally developed for the airborne NASA GISS
Research Scanning Polarimeter, is being adapted to the PACE observing system to allow for a
simultaneous retrieval of aerosol, thin cirrus, and ocean products using both PACE polarimeters
and the OCI shortwave infrared channels. Here, we describe the polarized ocean bio-optical model
we have developed for PACE-MAPP, which is designed to use a combination of homogenous and
coated spheres to more accurately model the absorption and backscattering properties of algal
and non-algal particles, and which also includes absorption by colored dissolved organic matter.

We first use Lorenz-Mie computations to create lookup tables to accurately and efficiently
characterize the optical properties of homogeneous and coated spheres embedded in water for
PACE. We then use these lookup tables to develop a bio-optical model that consists of an external
mixture of homogeneous (non-algal) and coated (algal) spheres. Lastly, we use the bio-optical
model in forward radiative transfer computations to perform inversions of MODIS remote sensing
reflectance for a variety of ocean regions. We explore the sensitivity of these inversions to ocean
constituent inherent optical properties.