Abstract Algae blooms have been a serious problem in coastal and inland water bodies across Canada. The temporal and spatial variability of algae blooms makes it difficult to use in situ monitoring of the lakes. This study aimed to evaluate the potential of Sentinel-3 Ocean and Land Color Instrument (OLCI) and Sentinel-2 Multispectral Instrument (MSI) data for monitoring algal blooms in Lake Erie. Chlorophyll-a (Chl-a)-related products of these sensors were tested by using the Great Lakes Chl-a NOAA’s monitoring data over summer 2016 and 2017, respectively. Our results show that while fluorescent light height (FLH) algorithm and models are limited to lakes with Chl-a < 8 mg/m3, maximum chlorophyll index (MCI) has the potential to be used effectively to monitor Chl-a concentration over Eutrophic lakes. Sentinel-3’s MCI is suggested for Chl-a > 20 mg/m3 and Sentinel-2 MCI for Chla > 8 mg/m3. Top of atmosphere (TOA) radiances showed a significantly better correlation with in situ data compared to TOA reflectance, which may be related to the poor pixel identification during the process of pixel flagging affected by the complexity of Case-2 water. Sentinel-2 MCI achieves better performance for Chl-a retrieval (R 2 = 0.92) than the existing methods. However, the FLH algorithms outperformed negative reflectance due to the shift of reflectance peak to longer wavelengths along with increasing Chl-a values.

中文翻译：

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利用 Sentinel-2 和 Sentinel-3 数据估算伊利湖西部盆地浮游植物叶绿素-a 浓度

摘要 藻华一直是加拿大沿海和内陆水体的严重问题。藻类大量繁殖的时间和空间变异性使得难以对湖泊进行原位监测。本研究旨在评估 Sentinel-3 海洋和陆地颜色仪器 (OLCI) 和 Sentinel-2 多光谱仪器 (MSI) 数据在监测伊利湖藻华方面的潜力。这些传感器的叶绿素-a (Chl-a) 相关产品分别使用五大湖 Chl-a NOAA 2016 年和 2017 年夏季的监测数据进行了测试。我们的结果表明，虽然荧光灯高度 (FLH) 算法和模型仅限于 Chl-a < 8 mg/m3 的湖泊，但最大叶绿素指数 (MCI) 有可能被有效地用于监测富营养化湖泊的 Chl-a 浓度. Chl-a 建议使用 Sentinel-3 的 MCI > 20 mg/m3 和 Sentinel-2 MCI 用于 Chla > 8 mg/m3。与TOA反射率相比，大气顶部（TOA）辐射与原位数据的相关性明显更好，这可能与Case-2水的复杂性影响像素标记过程中像素识别不良有关。Sentinel-2 MCI 在 Chl-a 检索 (R 2 = 0.92) 方面取得了比现有方法更好的性能。然而，由于反射峰值向更长波长移动以及 Chl-a 值增加，FLH 算法的性能优于负反射。这可能与Case-2水的复杂性影响像素标记过程中像素识别不良有关。Sentinel-2 MCI 在 Chl-a 检索 (R 2 = 0.92) 方面取得了比现有方法更好的性能。然而，由于反射峰值向更长波长移动以及 Chl-a 值增加，FLH 算法的性能优于负反射。这可能与Case-2水的复杂性影响像素标记过程中像素识别不良有关。Sentinel-2 MCI 在 Chl-a 检索 (R 2 = 0.92) 方面取得了比现有方法更好的性能。然而，由于反射峰值向更长波长移动以及 Chl-a 值增加，FLH 算法的性能优于负反射。