A new simplified method for the measurement of water-leaving radiance

Abstract

A new simplified method to measure water-leaving radiance was developed by combined use of a miniature spectrophotometer, a collimator, and a narrow pipe to block reflected sunlight from the sea surface. The instrument was handy, light-weighted and least expensive compared with those available for commercial use. The water-leaving radiance was determined by using the above-mentioned setup in the East China Sea, the Seto Inland Sea, and Shonai-ko of Lake Hamana. These areas covered a wide range of water mass types from clear to turbid water, and the new method was successfully implemented in all the areas. Signal to noise ratios of remote sensing reflectance R_rs measured by the instrument were satisfactorily small by taking running mean of 7 data readings over about 1.3 nm and by sampling of 1 nm interval. However, noises were not negligible in a low R_rs range below 0.001 sr ^-1 which occurred in the longer wavelength range than 650 nm. The estimated errors due to self-shading were satisfactorily small (< 5%) in the wavelength range from 400 to 590 nm.