中国近海非藻类颗粒对后向散射的影响研究

People monitor the optical-complexity water around the China Sea by the ocean color satellite, which is the important question to be solved for Chinese marine researcher. Base on the research of backscatter on the algae particles, this study discussed the particles affected the backscatter in the China Sea, focusing on the characteristics of the particles in the China Sea. We divide the particles into two parts. One is the algae particles, which include the phytoplankton and the organic particles changed by the phytoplankton. The other is the non-algae particles, which include the inorganic particles in the China Sea, such as suspended sediment. Base on the model of backscatter on the algae particles, we remove the backscatter coefficient of the algae particles from the backscatter coefficient of the particles. Then, we get the backscatter coefficient of the non-algae particles. We research the effect of the non-algae particles in backscatter by Mie scattering theory, which include the size and the chemical components of the non-algae particles. We find the relationship between the backscatter coefficient of the non-algae particles and the remote sensing reflectance, such as the backscatter coefficient on reference band and the attenuation index. Then, we get the model of backscatter on the non-algae particles around the China Sea and study the backscatter in the China Sea.

通过海洋水色卫星反演中国近海水体的复杂光学特性是中国近海科学定量化遥感亟待解决的重要问题。本项目在藻类颗粒后向散射研究的基础上，针对中国近海典型水体成分特点，对中国近海海水中影响水体后向散射的颗粒物进行研究。将水体中颗粒物的后向散射系数分为与浮游植物相协同变化的藻类颗粒(包括藻类颗粒和与藻类协同变化的有机颗粒)的后向散射系数和与浮游植物非协同变化的非藻类颗粒(中国近海以悬浮泥沙为主的无机颗粒等)。基于国外经典的藻类颗粒后向散射模型，从现场实际测量的总颗粒物后向散射系数中扣除掉藻类部分，得到非藻类颗粒的后向散射系数，基于Mie散射等理论进行分析，研究不同粒径和材质的非藻类颗粒对水体后向散射的影响，建立遥感反射率与非藻类颗粒的后向散射系数的关系(参考波段的后向散射系数和衰减指数)，建立中国近海非藻类颗粒后向散射模型，进而对中国近海典型水体后向散射后向散射进行研究。

本项目针对中国近海非藻类颗粒的后向散射无法估算等问题，创造性的提出中国近海水体可以分解为一类水体和陆源的非藻类颗粒、陆源的黄色物质的结合体。通过先模拟一类水体的水体光学辐射，后叠加陆源的非藻类颗粒和黄色物质的方式解决上述问题。首先，基于Mei散射理论对非藻类颗粒的后向散射进行理论计算，得出在可见光波段非藻类颗粒粒径小于3 um以下，粒径的后向散射在不同波段的后向散射系数随波段的增加呈现出指数下降（指数为Y），粒径大于3 um以上为无波段关系。再通过NOMAD数据集和中国近海数据集，对于Morel & Maritorena (2001，MM01)、Morel & Gentili(2007，MG07)、Mobley(2014，MO14)以及Hydrolight Abcase1模块(LUTs)等4种模型在全球和中国近海的适用性进行分析，得出MM01模型为最佳模型。基于中国近海的数据集，在MM01模型模拟的基础上，通过在总后向散射中扣除藻类颗粒的总结了非藻类后向散射系数及Y值与光谱的关系。通过结合MM01、陆源非藻类颗粒和黄色物质的经验关系及非藻类后向散射系数及Y值与光谱的关系，建立了中国近海后向散射的光谱模型。该模型能够在二类水体光学模型的半分析模型的建立，二类水体叶绿素算法和非藻类颗粒算法等方面起到理论的支持。