Performance of VIS/NIR and NIR Turbidity and Total Suspended Matter concentration algorithms in 3 turbid waters: Scheldt, Gironde, Río de la Plata

DOGLIOTTI, A.I.; RUDDICK, K.; KNAEPS, E.; RAYMAEKERS, D.; DOXARAN, D.; IBAÑEZ, G.; LAMARO, A.

Darmstadt

Encuentro; CoastColour and SeaSWIR User Consultation Meeting; 2013

Accurate estimation sediment concentration from remotely sensed data is of particular interest in coastal waters given the environmental and economic importance of sediment transport in these regions. Global algorithms for remotely estimating sediment concentrations are not currently available. Instead, many regional algorithms to estimate turbidity (T) and total suspended matter (TSM) concentration have been already developed (e.g. Doxaran et al. 2009, Nechad et al. 2009, 2010). In the frame of the SeaSWIR project in situ measurements of simultaneous water leaving reflectance, T and TSM concentration were carried out at three different highly turbid regions: Scheldt (Belgium), Gironde (France) and Río de la Plata (Argentina). In the present study the performance of existing one‐band and band‐ratio T and TSM ocean color remote sensing algorithms in these sites were tested. Two algorithms for retrieval of TSM were tested, a band ratio of MODIS red (645) and near infrared (859) bands (Doxaran et al. 2009), and a one‐band algorithm for the MODIS 859 band (Nechad et al. 2010). A similar one‐band algorithm was used to estimate T (Nechad et al. 2009, Dogliotti et al. 2011). A significant correlation was found between estimated and measured TSM (r>0.7) for both algorithms and all sites. However, for the band‐ratio algorithm some differences in the performance of the algorithm between sites were observed, while a general underestimation of field measurements was found for the single‐band algorithm at all sites. A better performance at all sites was found for the T algorithm, especially in the range between 10‐1000 FNU (r>0.8).Turbidity maps using the single‐band algorithm were derived from MODIS imagery available for the days corresponding to the La Plata and Gironde campaigns. The range and spatial variability of sediments in the sampled area was analyzed using the high resolution 250nm MODIS band. The analysis of HICO (Hyperspectral Imager for the Coastal Ocean) imagery acquired over La Plata region showed more detailed spatial variations of turbidity values evidencing the valuable information that can be retrieved given its high spatial resolution (~100m) and spectral characteristics. This sensor has some bands in the shortwave infrared part of the spectrum, like the 1020nm band present in Sentinel‐3/OLCI sensor, that can be used to retrieve T and/or TSM in highly waters as has been previously found (Knaeps et al. 2012).