A Spectral-Mixing Model for Estimating Sub-Pixel Coverage of Sea-Surface Floating Macroalgae

文献类型： 外文期刊

第一作者： Li, Lin

作者： Li, Lin;Zou, Jinqiu;Li, Lin;Zheng, Xiangyang;Wei, Zhenning;Xing, Qianguo;Zheng, Xiangyang;Wei, Zhenning;Xing, Qianguo

作者机构：

关键词： floating macroalgae; green tide; macroalgal blooms; Ulva prolifera; Sargassum horneri; sub-pixel coverage; GF-1; Yellow Sea

期刊名称：ATMOSPHERE-OCEAN （ 影响因子：2.058； 五年影响因子：1.698 ）

ISSN： 0705-5900

年卷期： 2018 年 56 卷 4 期

页码：

收录情况： SCI

摘要： In the past decade, floating macroalgae blooms have been increasing on a global scale. Sub-pixel coverage of floating macroalgae in a remote-sensing image is a crucial parameter for the estimation of biomass. In this study, in situ spectra of green macroalgae (Ulva prolifera), brown macroalgae (Sargassum horneri), and sea water were collected, and they were used to simulate the spectra of macroalgae-seawater mixtures in a linear mixing way. Three algae indices, normalized difference of vegetation index (NDVI), difference of vegetation index (DVI), and virtual-baseline reflectance height for floating algae (VB-FAH) derived from the spectra, were examined with the coverage of macroalgae. The results show that all three indices increase monotonically with increasing sub-pixel coverage of macroalgae: VB-FAH and DVI increase linearly, while NDVI shows a logarithmic increase. Based on this characteristic, two sub-pixel coverage models were proposed (i.e., a linear model based on VB-FAH (or DVI) and an exponential model based on NDVI). These models were then applied to the multiple-spectral GaoFen-1 (GF-1, 16m resolution) satellite image to examine the sub-pixel coverage of green tide in the Yellow Sea caused by the bloom of floating green macroalgae (U. prolifera). The results show that the relative differences between the two models are no more than 5%, indicating good consistency between the two models. Taking into account the sensitivity of these models (or indices) to the coverage of macroalgae, as well as atmospheric and sea surface conditions and their simplicity, we suggest using the linear model based on VB-FAH, DVI, or a similar band-difference index to estimate sub-pixel coverage of floating macroalgae.

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