Observação da pluma estuarina do Douro através de imagens MODIS de alta resolução

Resumo

The Douro is one of the longest rivers in the Iberian Peninsula and represents the most important freshwater input into the Atlantic Ocean in the north-western Portuguese coast. Episodes of strong rainfall intensify the river discharge, and promote the input of nutrients, and suspended matter in the continental shelf. The main goal of this study is to analyze the spatial and temporal variability of the Douro river turbidity plume. To achieve this purpose, daily high-resolution images of Moderate Resolution Imaging Spectroradiometer (MODIS - Aqua) normalized water-leaving radiance at 555 nm were processed, from level L1A to L2. The images with more than 70% of contaminated area due to clouds or other constraints were discarded. A region of interest (ROI) was defined from the river mouth to the continental slope in order to verify the amount of turbid pixels (>1.3 mWcm-2μm-1sr-1) in each image and to link it with the river discharge time series at Crestuma dam. Atmospherically corrected MODIS-Aqua data revealed strong seasonal variability in the area of the extension of the water plume, as well as in turbidity levels, which are significantly correlated with river discharge in a seasonal time scale.