Xi Ying, Du Ke-Ping, Zhang Li-Hua, Zhongping Lee, Li Xiao-Wen
Research Center for Remote Sensing and GIS, School of Geography, Beijing Normal University, State Key Laboratory of Remote Sensing Science, Beijing Key Laboratory for Remote Sensing of Environment and Digital Cities, Beijing 100875, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2010 Feb;30(2):489-94.
Previous researches on ocean optics and ocean color were based on the assumption that inherent optical properties and optically significant constituents of seawater are homogeneous in the vertical direction. However, oceanographic observations show that the assumption is not always exact and the vertical inhomogeneity of them exists in the upper ocean. The purpose of the present research is to study the effect of nonuniform vertical profiles of chlorophyll concentration on apparent optical properties with radiative transfer model Hydrolight. The vertical profiles of chlorophyll concentration were approximated according to a Gaussian function (Lewis et al, 1983). The apparent optical properties of seawater with nonuniform chlorophyll concentration profiles were simulated with Hydrolight radiative transfer model and case-1 bio-optical model, and then compared with those for homogenous ocean whose chlorophyll concentration was identical to the background chlorophyll concentration of inhomogenous cases. The results reveal that the subsurface maximal chlorophyll concentration increases the remote sensing reflectance at the blue wavelength and decreases it at the green wavelength, nonuniform vertical profiles of chlorophyll concentration change the diffuse attenuation coefficient profiles and the angular structure of the light field in the seawater, and the diffuse attenuation coefficients maximum and average cosines minimum appear at the depth of the maximal chlorophyll concentration.
以往关于海洋光学和海洋颜色的研究基于这样一种假设，即海水的固有光学特性和光学显著成分在垂直方向上是均匀的。然而，海洋学观测表明，这种假设并不总是准确的，它们在海洋上层存在垂直方向的不均匀性。本研究的目的是利用辐射传输模型Hydrolight研究叶绿素浓度的非均匀垂直分布对表观光学特性的影响。叶绿素浓度的垂直分布根据高斯函数进行近似（刘易斯等人，1983年）。利用Hydrolight辐射传输模型和一类生物光学模型模拟了叶绿素浓度分布不均匀的海水的表观光学特性，然后将其与叶绿素浓度与不均匀情况的背景叶绿素浓度相同的均匀海洋的表观光学特性进行比较。结果表明，次表层最大叶绿素浓度增加了蓝色波长处的遥感反射率，降低了绿色波长处的遥感反射率，叶绿素浓度的非均匀垂直分布改变了海水的漫衰减系数分布和光场的角度结构，漫衰减系数最大值和平均余弦最小值出现在最大叶绿素浓度深度处。
