AN EMPIRICAL ALGORITHM FOR LIGHT-ABSORPTION BY OCEAN WATER-BASED ON COLOR

Empirical algorithms for the total absorption coefficient and absorpti on coefficient by pigments for surface waters at 440 nm were developed by applying a quadratic formula that combines two spectral ratios of remote-sensing reflectance. For total absorption coefficients ranging from 0.02 to 2.0 m(-1), a goodness of fit was achieved between the mea sured and modeled data with a root-mean-square difference between the measured and modeled values for log10 scale (RMSDlog10) of 0.062 (15.3 % for linear scale, number of samples N = 63), while RMSDlog10 is 0.11 1 (29.1% for linear scale, N = 126) for pigment absorption (ranging fr om 0.01 to 1.0 m(-1)). As alternatives to pigment concentration algori thms, the absorption algorithms developed can be applied to the coasta l zone color scanner and sea-viewing wide-field-of-view sensor data to derive inherent optical properties of the ocean, For the same data se ts, we also directly related the chlorophyll a concentrations to the s pectral ratios and obtained an RMSDlog10 value of 0.218 (65.2% for lin ear scale, N = 120) for concentrations ranging from 0.06 to 50.0 mg m( -3). These results indicate that it is more accurate to estimate the a bsorption coefficients than the pigment concentrations from remotely s ensed data. This is likely due to the fact that for. the broad range o f waters studied the pigment-specific absorption coefficient at 440 nm ranged from 0.03 to 0.2 m(2) (mg chl)(-1). As an indirect test of the algorithms developed, the chlorophyll a concentration algorithm is ap plied to an independent global data set and an RMSDlog10 of 0.191 (55. 2% for linear scale, N = 919) is obtained. There is no independent glo bal absorption data set available as yet to test the absorption algori thms.