Application of a Semianalytical Algorithm to Remotely Estimate Diffuse Attenuation Coefficient in Turbid Inland Waters

Remote estimation of the vertically averaged diffuse attenuation coefficient over a water layer K̅_d(λ) is of great importance in understanding and modeling the physical, chemical, and biological processes in water bodies. A semianalytical algorithm was previously proposed to remotely estimate K̅_d( λ) based on the retrieval of the total absorption and backscattering coefficients ( a and bb ). The algorithm has been effectively applied to clear and slightly turbid oceanic waters, but its applicability in turbid inland waters is still unknown. In this study, the relationship between a and bb on the one hand with K̅_d(λ) used in the semianalytical algorithm was first validated by the measured a and bb. Second, the semianalytical algorithm was combined with the so-called QAA_Turbid (quasi-analytical algorithm for turbid waters) to remotely estimate K̅_d(λ) for highly turbid waters. We tested the performance of the combined algorithm at wavelengths of 443, 556, and 669 nm by using a data set collected from a turbid lake in Japan. The validation results demonstrated that it could estimate K̅_d(λ) (ranging from 1.94 to 9.47 m^-1) with root-mean-square error and relative error values of 0.17 and 12.96%, respectively. These results indicate the great potential of the semianalytical algorithm to accurately monitor the spectra of K̅_d(λ) for turbid inland waters from satellite observations.