Retrieval of Inherent Optical Property in Optically Shallow Waters

Standard ocean color algorithms for the retrieval of inherent optical properties (IOPs) either utilize spectral band ratios or inversion models tuned for the open ocean. However, such algorithms are known to fail in optically shallow waters, where bottom reflected light can contribute significantly to the water leaving radiance. Recently the SWIM algorithm was developed for improved retrievals of IOPs in optically shallow waters. This algorithm requires as input known bathymetric and substrate reflectance data that are often unknown and temporally variable for a region of interest. Here, we extend the applicability of the HOPE shallow water inversion model for the retrieval of IOPs in optically shallow waters with MODIS Aqua imagery. We investigate two approaches: (1) the use of coincident MERIS-derived bathymetry as a known input parameter to HOPE, and; (2) the inclusion the 469-, 555- and 645-nm MODIS bands without fixing any HOPE parameters to known values. With a MODIS Aqua image of the Great Bahamas Bank as an example, we compare the retrievals of a_phy(443), a_dg(443) and b_bp(443) from HOPE, SWIM and the GIOP and show that both aforementioned approaches provide temporal and spatial consistency within optically shallow water regions and between adjacent optically deep waters. Although both methods provide similar results the second approach is favored due to its independence from MERIS data.