An evaluation of apparent color of seawater based on the in-situ and satellite-derived Forel-Ule color scale
An evaluation of apparent color of seawater based on the in-situ and satellite-derived Forel-Ule color scale
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DOI：
10.1016/j.ecss.2020.107032
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发表时间：
2020-11-05
影响因子：
2.8
通讯作者：
Lv, Xianqing
中科院分区：
文献类型：
--
作者：
Nie, Yafei;Guo, Junting;Lv, Xianqing
海水的表观颜色是描述海水光学特性的关键变量，在理解海洋表层生态系统和过程中起着至关重要的作用。传统上由手持Forel-Ule比色仪标度确定的海水表观颜色，现在可以由卫星海洋颜色最终产品水离开辐射或遥感反射率得出。然而，这种检索算法尚未在中国近海沃茨中得到验证，这是世界上最浑浊的沃茨之一。因此，卫星导出的Forel-Ule指数（FUI卫星）的精度在这一领域是未知的。本文利用我国首次大规模海洋环境系统调查中的现场FUI（FUI insitu）观测资料，对FUI卫星值进行了估算，结果表明，二者总体上符合较好（r = 0.75，N = 2390，p = 0.00，MAD = 2.61，MUPD = 35.02%）。研究了东海沿岸和北部湾沿着的卫星导频变化。此外，FUI卫星的不确定性概率作为FUI原位的函数可以用高斯函数很好地拟合（r（2）= 0.99）。研究还表明，以线性函数为基函数的径向基函数是FUIinsitu空间插值的最佳方法。FUI卫星与内插的FUI原位场仍有较好的一致性（r = 0.77，N = 265302，p = 0.00，MAD = 1.73，MUPD = 36.06%），表明遥感技术可以作为中国近海沃茨环境监测的一种综合工具。
Apparent color of seawater is a key variable that can be used to describe the optical properties of seawater and plays a crucial role in understanding surface marine ecosystems and processes. The apparent color of seawater traditionally determined from a hand-held Forel-Ule color comparator scale can now be derived from satellite ocean color end-product water leaving radiance or remote sensing reflectance. However, this retrieval algorithm has not been verified in China's offshore waters, which are some of the most turbid waters in the world. Thus, the precision of the satellite-derived Forel-Ule index (FUIsatellite) is unknown in this area. In this paper, FUIsatellite values is evaluated using in-situ FUI (FUIinsitu) observations obtained in the first large-scale systematic survey on the marine environment in China, and the results show that there is a generally good agreement (r = 0.75, N = 2390, p = 0.00, MAD = 2.61, MUPD = 35.02%) between them. Uncertainties of satellite derivation along the coast of the East China Sea (ECS) and the Beibu Gulf are identified. Moreover, the probability of uncertainties of FUIsatellite as a function of FUIinsitu can be well fitted by Gaussian function (r(2) = 0.99). Our study also demon-strates that the radial basis function, which uses linear function as the basis function, is the optimal method on the spatial interpolation of FUIinsitu. The FUIsatellite is still in good agreement with the interpolated FUIinsitu field (r = 0.77, N = 265302, p = 0.00, MAD = 1.73, MUPD = 36.06%), which reveals that remote sensing techniques could be an integral tool for operational environmental monitoring of water quality in China's offshore waters.