POSTER Session 2

SIMULATING HYPERSPECTRAL REFLECTANCES UNDER DIFFERENT SUBSURFACE THICKNESSES OF UPWELLED WATERS

Understanding in-water optical properties is essential to improve the knowledge of oceanographic processes, such as coastal upwelling, detected by the new era of operational hyperspectral remote sensing sensors. This work investigates the variability of the above surface and underwater hyperspectral light field, focusing on the effects of subsurface intrusions of the South Atlantic Central Water (SACW) on the coastal region of São Paulo/Brazil. SACW can transport significant amounts of colored dissolved organic matter (CDOM) and high phytoplankton biomass subsuperficially. In situ measurements were performed in a case II site located at São Sebastião Channel, and in case I waters near the Alcatrazes archipelago in the inner continental shelf. In-situ optical profiles were carried out simultaneously with above and in-water radiometric measurements. Discrete samples in three depths (surface, bottom, and at an intermediary depth) were taken to quantify CDOM and algal light absorption coefficients. Hydrolight simulations were carried out to explore the impact of distinct thicknesses of SACW within the water column. Preliminary results show that Case II water columns 30 % SACW dominated at 5 meters depth up to 80 % SACW dominated at 40 meters depth have a significant decrease in the surface Remote Sensing Reflectance (Rrs-sup) when compared to a homogeneous 20 % SACW dominated water column. Future results will also focus on differentiating the Case I/Case II SACW impact for Rrs-sup, to investigate the feasibility of SACW detection from orbital hyperspectral sensors.

Lino Augusto Sander de Carvalho, Federal University of Rio de Janeiro (UFRJ), Brazil, https://orcid.org/0000-0001-8839-5366

Daniel Maciel, National Institute for Space Research (INPE), Brazil

Luiz Fernando Albuquerque Bruno, Federal University of Rio de Janeiro (UFRJ), Brazil

Claudio Barbosa, National Institute for Space Research (INPE), Brazil

Mauro Cirano, Federal University of Rio de Janeiro (UFRJ), Brazil

Ronaldo Christofoletti, Federal University of São Paulo (UNIFESP), Brazil

Aurea Ciotti, Marine Biology Center (CEBIMAR), University of São Paulo, Brazil

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