Spectral radiance measurements during a Nodularia spumigena bloom event on Lake Bante in Wilhelmshaven, Germany

Hyperspectral radiance observations were made from a small electric motor powered boat on Lake Bante in Wilhelmshaven, Germany during a Nodularia spumigena bloom event. The observations were completed on 25 August 2022 using a Spectral Evolution (SEV) SR-3501 spectroradiometer covering the wavelength range 280 nm to 2500 nm. SEV was operated in calibrated radiance mode with an 8° field-of-view lens fitted. Each measurement was generated as the mean of 20 scans. At each station, a series of 3 calibrated radiance measurements were done over the unique optical active targets (i) a 20 × 20 cm SphereOptics Zenith Polymer® SG3120 ≈ 99 % full material PTFE diffuse standard panel = Ed, (ii) lake water surface = Lsfc and then (iii) sky = Lsky at a ~45° viewing angle from nadir. The series of observations at each station was repeated at most 6 times. The measurements were completed at an azimuthal angle from sensor heading to the sun within the range 90 - 135° to avoid surface reflectanced (Garaba and Zielinski, 2013). Quality control step managed to obtain a set of at least 3-6 pseudo replicate measurements for the sampled stations as some measurements were affected by drift and rotation of the boat that resulted in non-optimal viewing geometry or presence of surface reflected glint.

本数据集的高光谱辐射亮度观测于2022年8月25日在德国威廉港班特湖的一艘小型电动船上完成，采集时段正值泡沫节球藻（Nodularia spumigena）水华暴发事件。观测采用光谱演化（Spectral Evolution，SEV）SR-3501型光谱辐射计，覆盖280 nm至2500 nm的波段范围。该辐射计以校准辐射亮度模式运行，搭载8°视场镜头，单次测量结果为20次扫描的平均值。每个观测站点开展3组针对不同光学活性靶标的校准辐射亮度测量：(i) 20×20 cm的SphereOptics Zenith Polymer® SG3120型漫反射标准面板（约99%纯聚四氟乙烯（PTFE）材质，对应下行辐照度Ed）；(ii) 湖面水体（对应水面辐亮度Lsfc）；(iii) 以相对于天底方向约45°的观测角测量的天空辐亮度Lsky。每个站点的观测序列最多重复6次。为规避水面镜面反射耀斑的干扰，观测时设置传感器指向与太阳的方位角介于90°至135°之间（Garaba和Zielinski，2013）。受船体漂移与转动影响，部分测量存在非最优观测几何或水面反射耀斑干扰，经质量控制步骤处理后，最终为每个采样站点保留了至少3~6组伪重复测量结果。