engleski

Effect of suspended particulate-size distribution on the backscattering ratio in remote sensing of seawater

Mie theory is used to study the influence of particle size distribution (PSD) on backscattering ratio for case 1 and case 2 waters. Several in situ measured PSD from coastal water and open ocean, representing typical case 2 and case 1 waters were used in this investigation. Calculation of backscattering ratio requires integration of PSD over much broader size range than usually measured. Consequently, extrapolation from fitted data is necessary. To that purpose, the measured data were fitted with hyperbolic (Junge) and the two component model of PSD. It is shown that the result of extrapolation, hence backscattering ratio, critically depends on chosen PSD model. For a particular PSD model the role of submicron particles and applied integration limits on backscattering ratio are discussed. The use of hyperbolic particle size distribution model largely overestimates number of small (submicron) particles, that significantly contribute to the backscattering and consequently leads to an erroneously high backscattering ratio. The two component model proves to be adequate PSD model for use in backscattering/scattering calculations providing satisfactory results complying with experimental data. The results are relevant for the inversion of remotely sensed data and prediction of optical properties and concentration of phytoplankton pigments, suspended sediment, and yellow substance.

backscattering ; particle-size distribution ; seawater ; remote sensing

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