Detecting Sargassum Bloom Directly From Satellite Top-of-Atmosphere Reflectance With High-Resolution Images
IEEE Transactions on Geoscience and Remote Sensing（2023）
摘要
Massive floating Sargassum blooms have occurred frequently in many parts of the global ocean, and satellite remote sensing provides an effective way to monitor their spatiotemporal variation. However, coarse-resolution satellite data often suffer from a data gap in nearshore waters and detection uncertainty of Sargassum amount especially for smaller patches. These limitations may be ameliorated by high-resolution satellite data, yet such great potential is hindered by the lack of reliable and easy-to-implement methods to detect Sargassum slicks. Here, combining the visible and near-infrared top-of-atmosphere reflectance ( R TOA ) data with random forest model, a new method namely the R TOA -RF model was designed to automatically detect Sargassum from high-resolution satellite imagery with four wavebands. Specifically, this model was successfully applied to various satellite sensors, including Gaofen1-Wide Field View Multispectral Camera (WFV; 16m), GF2 - Multispectral Scanner (4m), Gf6-WFV (16m), Huanjing1A/B - Charge Coupled Device (30m), Haiyang1C/D - Coastal Zone Imager (50m). Comparisons with visual inspection and cross-index indicated that all achieved satisfactory performance for detecting Sargassum slicks, with the overall accuracy and Kappa values greater than 96% and 88% respectively. The sensitivity analysis of the model as example of different sensors suggested the R TOA -RF model can effectively identify Sargassum features under complex ocean background, cloud cover and sun glint, even under conditions of surface wave glitter and weak Sargassum feature with low false positive rate (<9.60%). The findings here not only pave the way for operational monitoring fine-scale Sargassum , but importantly provide thought for developing detection method of macroalgae blooms in global water.
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关键词
bloom,satellite,top-of-atmosphere,high-resolution
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