Assessment of VIIRS on the Identification of Harmful Algal Bloom Types in the Coasts of the East China Sea

Abstract

Visible Infrared Imaging Radiometer Suite (VIIRS) data were systematically evaluated and used to detect harmful algal bloom (HAB) and classify algal bloom types in coasts of the East China Sea covered by optically complex and sediment-rich waters. First, the accuracy and spectral characteristics of VIIRS retrieved normalized water-leaving radiance or the equivalent remote sensing reflectance from September 2019 to October 2020 that were validated by the long-term observation data acquired from an offshore platform and underway measurements from a cruise in the Changjiang Estuary and adjacent East China Sea. These data were evaluated by comparing them with data from the Moderate-Resolution Imaging Spectroradiometer. The bands of 486, 551, and 671 nm provided much higher quality than those of 410 and 443 nm and were more suitable for HAB detection. Secondly, the performance of four HAB detection algorithms were compared. The Ratio of Algal Bloom (RAB) algorithm is probably more suitable for HAB detection in the study area. Importantly, although RAB was also verified to be applicable for the detection of different kinds of HAB (Prorocentrum donghaiense, diatoms, Ceratium furca, and Akashiwo sanguinea), the capability of VIIRS in the classification of those algal species was limited by the lack of the critical band near 531 nm.

Evaluation of Rayleigh-Corrected Reflectance on Remote Detection of Algal Blooms in Optically Complex Coasts of East China Sea

“…For the purpose of match-up comparison analysis, Lwn and Rrs data were selected at specific center wavelengths: 412, 442, 490, 510, 560, 620, 667, 779, and 865 nm. To leverage the high-frequency measurements provided by SeaPRISM, the in situ data used for the quantitative matchup comparison analysis were carefully chosen, ensuring they corresponded to the measurements made within a narrow (±0.5 h) time window surrounding the satellite overpass time at the Dongou site [60]. This approach minimized potential biases introduced by the rapid dynamic changes observed in coastal waters.…”