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- Title
Evaluation of Unified Algorithms for Remote Sensing of Chlorophyll-a and Turbidity in Lake Shinji and Lake Nakaumi of Japan and the Vaal Dam Reservoir of South Africa under Eutrophic and Ultra-Turbid Conditions.
- Authors
Sakuno, Yuji; Yajima, Hiroshi; Yoshioka, Yumi; Sugahara, Shogo; Abd Elbasit, Mohamed A. M.; Adam, Elhadi; Chirima, Johannes George
- Abstract
We evaluated unified algorithms for remote sensing of chlorophyll-a (Chla) and turbidity in eutrophic and ultra-turbid waters such as Japan’s Lake Shinji and Lake Nakaumi (SJNU) and the Vaal Dam Reservoir (VDR) in South Africa. To realize this objective, we used 38 remote sensing reflectance (<italic>Rrs</italic>), Chla and turbidity datasets collected in these waters between July 2016 and March 2017. As a result, we clarified the following items. As a unified Chla model, we obtained strong correlation (R2 = 0.7, RMSE = 2 mg m−3) using a two-band model (2-BM) and three-band model (3-BM), with <italic>Rrs</italic>(687)/<italic>Rrs</italic>(672) and [<italic>Rrs</italic>−1(687) − <italic>Rrs</italic>−1(672)] × <italic>Rrs</italic>(832). As a unified turbidity model, we obtained strong correlation (R2 = 0.7, RMSE = 260 NTU) using 2-BM and 3-BM, with <italic>Rrs</italic>(763)/<italic>Rrs</italic>(821) and <italic>Rrs</italic>(810) − [<italic>Rrs</italic>(730) + <italic>Rrs</italic>(770)]/2. When targeting the Sentinel-2 Multispectral Imager (MSI) frequency band, we focused on MSI Bands 4 and 5 (<italic>Rrs</italic>(740) and <italic>Rrs</italic>(775)) for the Chla algorithm. When optically separating SJNU and VDR data, it is effective to use the slopes of MSI Bands 3 and 4 (<italic>Rrs</italic>(560) and <italic>Rrs</italic>(665)) and the slopes of MSI Bands 7 and 9 (<italic>Rrs</italic>(775) and <italic>Rrs</italic>(865)).
- Subjects
SHINJI Lake (Japan); SOUTH Africa; CHLOROPHYLL; ALGORITHMS; LAKES; TURBIDITY currents
- Publication
Water (20734441), 2018, Vol 10, Issue 5, p618
- ISSN
2073-4441
- Publication type
Article
- DOI
10.3390/w10050618