Using ocean colour remote sensing products to estimate turbidity at the Wadden Sea time series station Spiekeroog

Abstract

Time series measurements at the Wadden Sea time series station Spiekeroog (WSS) in the southern North Sea were used to empirically develop approaches for determining turbidity from ocean colour remote sensing products (OCPs). Turbidity was observed by a submerged optical sensor. Radiometric quantities were collected using hyperspectral radiometers. Surface reflected glint correction was applied to the radiometric quantities to compute remote sensing reflectance (R RS ) and the R RS was converted into perceived colour of seawater matching the Forel-Ule colour Index (FUI) scale. The empirical approaches for determining turbidity from OCPs showed good least squares linear correlations and statistical significance (R 2 > 0.7, p < 0.001). These OCP approaches had relatively low uncertainties in predicting turbidity with encouraging mean absolute percent difference less than 31 %. The problem of bio-fouling on submerged sensors and the potential application of OCPs to monitor or correct for sensor drifts was evaluated. A protocol is proposed for the acquisition and processing of hyperspectral radiometric measurements at this optically complex station. Use of the classic FUI as a time series indicator of surface seawater changes did show promising results. The application of these OCPs in operational monitoring changes in water quality was also explored with the aim to evaluate the potential use of the WSS datasets in calibration and validation of satellite ocean colour remote sensing of these very turbid coastal waters.

Influence of solar radiation on biogeochemical parameters and fluorescent dissolved organic matter (FDOM) in the sea surface microlayer of the southern coastal North Sea

“…Intensities of GHI were recorded at the Times-series Station Spiekeroog (TSS) with TriOS RAMSES hyperspectral radiometers (TriOS GmbH, Rastede, Germany). All data were interpolated every 5 nm between 305 and 405 nm (Garaba et al, 2014a). PAR corresponds to the spectral wave band of solar radiation from 400 to 700 nm that photoautotrophic organisms are able to utilize for photosynthesis.…”

The Coastal Observing System for Northern and Arctic Seas (COSYNA)

“…An ensemble of sun glint detection methods improves the flagging performance of the data quality algorithm (Garaba et al, 2015a). Remote sensing spectra of good quality are used to derive in-water constituents like chlorophyll, coloured dissolved organic matter, and suspended particulate matter along cruise tracks in the North West European Shelf Sea (Garaba et al, 2014b) and Arctic (Garaba et al, 2013a), and at a time-series station in the Wadden Sea (Garaba et al, 2014a). A very recent application is the calculation of the Forel-Ule Colour Index from reflectance spectra, which opens up the possibil- Figure 21.…”

The effect of dispersed Petrobaltic oil droplet size on photosynthetically active radiation in marine environment

“…Changes in the light flux in seawater affect the apparent optical properties (AOPs) measured by remote sensors, both offshore and satellite (Garaba et al 2014;Hieronymi 2013). Most commonly derived AOPs are the remote sensing reflectance R rs (λ), the attenuation coefficient K d , the water leaving radiance L w , downwelling irradiance E d (z) and the diffuse reflectance R(λ,z), and their ratios applied, e.g.…”