Remote sensing of phytoplankton pigments: a comparison of empirical and theoretical approaches

被引:238
作者
Sathyendranath, S [1 ]
Cota, G
Stuart, V
Maass, H
Platt, T
机构
[1] Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4J1, Canada
[2] Fisheries & Oceans Canada, Bedford Inst Oceanog, Div Biol Oceanog, Dartmouth, NS B2Y 4A2, Canada
[3] Old Dominion Univ, Ctr Coastal Phys Oceanog, Norfolk, VA 23529 USA
基金
加拿大自然科学与工程研究理事会;
关键词
D O I
10.1080/014311601449925
中图分类号
TP7 [遥感技术];
学科分类号
081102 ; 0816 ; 081602 ; 083002 ; 1404 ;
摘要
Algorithms that have been used on a routine basis for remote sensing of the phytoplankton pigment, chlorophyll-a, from ocean colour data from satellite sensors such as the CZCS (Coastal Zone Color Scanner), SeaWiFS ( Sea Viewing Wide Field-of-View Sensor) and OCTS (Ocean Colour and Temperature Scanner) are all of an empirical nature. However, there exist theoretical models that allow ocean colour to be expressed as a function of the inherent optical properties of seawater, such as the absorption coefficient and the backscattering coefficient. These properties can in turn be expressed as functions of chlorophyll-a, at least for the so-called Case 1 waters in which phytoplankton may be considered to be the single, independent variable responsible for most of the variations in the marine optical properties. Here, we use such a theoretical approach to model variations in ocean colour as a function of chlorophyll-a concentration, and compare the results with some empirical models in routine use. The parameters of phytoplankton absorption necessary for the implementation of the ocean colour model are derived from our database of over 700 observations of phytoplankton absorption spectra and concurrent measurements of phytoplankton pigments by HPLC (High Performance Liquid Chromatography) techniques. Since there are reports in the literature that significant differences exist in the performance of the algorithms in polar regions compared with lower latitudes, the model is first implemented using observations made at latitudes less than 50 degrees. It is then applied to the Labrador Sea, a high-latitude environment. Our results show that there are indeed differences in the performance of the algorithm at high latitudes, and that these differences may be attributed to changes in the optical characteristics of phytoplankton that accompany changes in the taxonomic composition of their assemblages. The sensitivities of the model to assumptions made regarding absorption by coloured dissolved organic matter (or yellow substances) and backscattering by particles are examined. The importance of Raman scattering on ocean colour and its influence on the algorithms are also investigated.
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页码:249 / 273
页数:25
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