Approach for identifying optically shallow pixels when processing ocean-color imagery.

Area of Science:

• Oceanography
• Remote Sensing
• Geophysics

Background:

• Ocean-color remote sensing derives marine geophysical parameters from water-leaving radiances.
• Optically shallow regions, like coral reefs and sand banks, can bias ocean color data due to seafloor reflections.
• Current methods often mask these areas using only bathymetric data.

Purpose of the Study:

• To develop an improved method for flagging optically shallow pixels in ocean color datasets.
• To account for bathymetry, water clarity, and seafloor albedo in identifying optically shallow areas.
• To enhance the quality control of derived ocean color products.

Main Methods:

• Developed a new approach to flag optically shallow pixels by integrating bathymetry, water clarity, and seafloor albedo.
• Predicted water column optical depth at 547 nm (ζ(547)) from bathymetric and optical properties.
• Used radiative transfer modeling to establish a threshold (ζ(547) = 20) for flagging, also flagging waters shallower than 5m.

Main Results:

• The new method successfully flags potentially optically shallow pixels by considering multiple factors.
• Radiative transfer modeling identified a conservative threshold for flagging based on seafloor reflectance.
• Analysis showed varying bathymetric datasets can influence the optically shallow flag.

Conclusions:

• The developed optically shallow flag enhances the quality control of ocean color data products.
• This flag can be utilized to switch between algorithms for optically deep and shallow waters.
• The method provides a more robust approach to handling seafloor reflectance contamination in remote sensing data.