Institute of Hydroecology, Ministry of Water Resources and Chinese Academy of Sciences, Wuhan, China; Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, UK.
Pixalytics Ltd., Plymouth Science Park, 1 Davy Road, Plymouth, UK; School of Marine Science and Engineering, University of Plymouth, Drake Circus, Plymouth, UK.
Sci Total Environ. 2017 Dec 1;601-602:1060-1074. doi: 10.1016/j.scitotenv.2017.05.245. Epub 2017 Jun 9.
A novel approach, termed Summed Positive Peaks (SPP), is proposed for determining phytoplankton abundances (Chlorophyll-a or Chl-a) and surface phytoplankton bloom extent in the optically complex Baltic Sea. The SPP approach is established on the basis of a baseline subtraction method using Rayleigh corrected top-of-atmosphere data from the Medium Resolution Imaging Spectrometer (MERIS) measurements. It calculates the reflectance differences between phytoplankton related signals observed in the MERIS red and near infrared (NIR) bands, such as sun-induced chlorophyll fluorescence (SICF) and the backscattering at 709nm, and considers the summation of the positive line heights for estimating Chl-a concentrations. The SPP algorithm is calibrated against near coincident in situ data collected from three types of phytoplankton dominant waters encountered in the Baltic Sea during 2010 (N=379). The validation results show that the algorithm is capable of retrieving Chl-a concentrations ranging from 0.5 to 3mgm, with an RMSE of 0.24mgm (R=0.69, N=264). Additionally, the comparison results with several Chl-a algorithms demonstrates the robustness of the SPP approach and its sensitivity to low to medium biomass waters. Based on the red and NIR reflectance features, a flagging method is also proposed to distinguish intensive surface phytoplankton blooms from the background water.
提出了一种新的方法，称为总和正峰（SPP），用于确定波罗的海光学复杂区域浮游植物丰度（叶绿素-a 或 Chl-a）和表面浮游植物爆发范围。SPP 方法基于使用来自中等分辨率成像光谱仪（MERIS）测量的瑞利校正的大气顶部数据的基线减法方法建立。它计算了 MERIS 红色和近红外（NIR）波段中观察到的与浮游植物相关的信号之间的反射率差异，例如太阳诱导的叶绿素荧光（SICF）和 709nm 处的后向散射，并考虑了正线高度的总和以估计 Chl-a 浓度。SPP 算法通过与 2010 年在波罗的海遇到的三种浮游植物优势水域的近实时数据（N=379）进行对比校准。验证结果表明，该算法能够检索 0.5 至 3mgm 范围内的 Chl-a 浓度，RMSE 为 0.24mgm（R=0.69，N=264）。此外，与几种 Chl-a 算法的比较结果表明，SPP 方法具有稳健性，并且对低至中等生物量水域具有敏感性。基于红和近红外反射特征，还提出了一种标志方法来区分高强度的表面浮游植物爆发和背景水。
