Preliminary Study on the In-Water Spectral Property and Bio-Optical Algorithm in Taiwan Waters

Abstract

本研究之目的係為究明臺灣沿岸水域及外洋水域的水中物質對其水中光學性質之影 響，使用水中輻射光譜儀計測剖層海水中光譜波長350nm至720nm的向下及向上輻射照度， 並步於各水層進行採水，分析水中的葉綠素a、總色素（葉綠素a及褐色素）及總懸浮物等之 濃度，以探討影響水中輻射照度分布曲線之原因。研究結果顯示，總色素濃度與葉綠素a濃 度及總懸浮物濃度呈現明顯的正相關，而水中光學深度則與總色素濃度、葉綠素a濃度及總 懸浮物濃度呈現明顯的負相關。黑潮域與沿岸水的水中輻射光譜曲線之形狀呈顯著的差異， 使得水中輻射照度分布曲線於412、443、490、520、550、555及670nm波段處出現了屈折 點。使用此些波段之Eu(0,λ1)/Eu(0,λ2)比值完成水色模式演算，對葉綠素a之水色模式，以 Eu(490)/ Eu(510) (r2>0.983)、Eu(490)/ Eu(555) (r2>0.943)最佳，對總色素（葉綠素a加褐色素） 之水色模式，以Eu(490)/ Eu(510) (r2>0.983)、Eu(412)/ Eu(555) (r2>0.957)及Eu(490)/ Eu(555) (r2>0.947)最佳，對總懸浮物之水色模式，以Eu(412)/ Eu(490) (r2>0.929)、Eu(412)/ Eu(510) (r2>0.915)、Eu(412)/ Eu(555) (r2>0.886)及Eu(490)/ Eu(510) (r2>0.875)較佳。 The purpose of study is to improve our understanding of the effects of in-water chlorophyll a, total pigment and total suspended matter (TSM) on the optical properties of coastal water and oceanic water around Taiwan. An underwater spectroradiometer is used to measure the vertical profile of the downwelling and the upwelling irradiance in the visible 400 nm to 700 nm wavelengths in the coastal and offshore waters around Taiwan. The results show that the relationship to total pigment against chlorophyll a and TSM shows a exponential function. The relationship of optic depth against chlorophyll a, total pigment and TSM shows inverse exponential function. Shapes of spectral distribution courve in pure Kuroshio region and coastal waters are obviously different. Some inflection points in spectral distribution curve appear at wavelength bands of 412, 443, 490, 520, 550, 555 and 670 nm. Using irradiance ratio of Eu(0,λ1)/Eu(0,λ2), some better bio-optical algorithms are obtained. For chlorophyll a algorithm, Eu(490)/ Eu(510) (r2>0.983) and Eu(490)/ Eu(555) (r2>0.943) are good. For total pigment algorthm, Eu(490)/ Eu(510) (r2>0.983), (r2>0.957) and Eu(490)/ Eu(555) (r2>0.947) are suitable. For TSM algorithm, Eu(412)/ Eu(490) (r2>0.929), Eu(412)/ Eu(510) (r2>0.915), Eu(412)/ Eu(555) (r2>0.886), Eu(490)/ Eu(510) (r2>0.875) Eu(490)/ Eu(555) (r2>0.820) are suitable for this study.