The water quality products are generated with the ACOLITE atmospheric (Dark Spectrum Fitting, DSF) and sunglint correction software (Vanhellemont, 2019) at 10 m spatial resolution. The standard products to monitor the biogeochemical conditions in the Doñana Region are seawater turbidity (FNU) and chlorophyll-a (chl-a, mg/m³). Both indicators are required by the EU Water Framework Directive (WFD) for the evaluation of the good ecological status of the coastal regions. The Nechad et al. (2009) semi-analytical algorithm (red band, Rrs 665 nm) is applied to estimate turbidity with both satellites and the OC3 algorithm was applied to calculate the concentration of seawater chlorophyll-a (O'Reilly &Werdell, 2019). 

Products description

Cloud Coverage: RGB image from Sentinel-2A/B designed to provide cloud coverage information at the moment of satellite overflight. Chl-a, SPM and TUR maps availability is subjected to cloud coverage. When no data is available for these ocean colour variables, please refer to this RGB image to assess the cloudiness of the moment the images were taken. We also provide the shapefile of the region to better interpret completely cloud-covered skies, which otherwise will appear as a white image.

Surface Chlorophyll-a concentration (CHL-A): product expressed here in mg/m³, is retrieved via a multi-algorithm approach with optimized quality flagging. We used the commonly OC3 algorithm (O'Reilly et al., 2019)

Solid Particulate Matter (SPM): product expressed in g/m³, is retrieved through the Sentinel-2 following Nechad et al., (2010) methodology.

Turbidity (TUR): product expressed in g/m³, is retrieved through the Sentinel-2 following Nechad et al., (2010) methodology.

 

References

• Nechad, B.; Ruddick, K.; Neukermans, G. Calibration and validation of a generic multisensor algorithm for mapping of turbidity in coastal waters. In: SPIE Europe Remote Sensing. International Society for Optics and Photonics 2009, pp. 74730H–74730H.
• O'Reilly, J.E.; Werdell, P.J. Chlorophyll algorithms for ocean color sensors - OC4, OC5 & OC6. Remote Sensing of Environment 2019, 229, 32-47.
• Vanhellemont, Q. Adaptation of the dark spectrum fitting atmospheric correction for aquatic applications of the Landsat and Sentinel-2 archives. Remote Sensing of Environment 2019, 225, 175-192.