Ocean Color Determination Through a Scattering Atmosphere

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Abstract
Measurements made of the surface level albedo for ocean water containing various concentrations of phytoplankton indicate a strong correlation between wavelength dependent albedo ratios and phytoplankton chlorophyll concentration. To sense surface level albedo ratios from space platforms it is necessary to correct for the scattering and absorption properties of the atmosphere for the wavelengths in question. Atmospheric scattering models were constructed to calculate corrections at two wavelengths, 0.46 μm and 0.54 μm. The relationship between albedo ratios at the top of the atmosphere and at surface level was made for several different aerosol optical depths. Assuming a natural background uncertainty in the aerosol optical depth of 0.1 it is found that the chlorophyll concentration may be determined to within one standard deviation of from 0.5 mg to 2.5 mg/m3, depending upon the solar zenith angle at the time of measurement. By remotely sensing the aerosol optical depth to a greater accuracy it appears feasible to detect chlorophyll concentrations to an uncertainty approaching 0.1 mg/m3.