Fig 1.
Localization of the study area.
Tagus River mouth is located between capes Espichel and Raso (Tagus ROFI area). D marks the position of the Almourol station where river discharge data was obtained. W indicates the point where wind data were acquired. T represents the area of Cascais where tidal data was predicted. Grey and pink lines mark the alongshore and cross-shore transects used to analyze turbidity. Service Layer Credits Source: Esri, DigitalGlobe, GeoEye, icubed, Earthstar, Geographics, CENS/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community.
Table 1.
Comparison of the different available bands for the Aqua and Terra satellites.
Fig 2.
(a) Annual hydrologic cycle for Tagus River discharge (m3s-1) obtained from 2003 to 2015. Solid black line: monthly average; the line inside each box indicates the median; lower and upper whiskers: minimum and maximum, respectively; lower and upper box limits: first and third quartiles, respectively, (b) Wind rose (ms-1) of the Tagus ROFI during the period of 2003 to 2015, (c) Surface elevation of seawater at Cascais for 2007. Solid lines represent the limits of high and low tide and, (d) Daily tidal amplitude at Cascais for 2007. The solid lines indicate the limits of spring and neap tides.
Table 2.
Main synoptic conditions analyzed in the study.
Fig 3.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images under high river discharge (> 66th percentile) during 2003.
Results compare the effect of atmospheric corrections using NIR (a) and SWIR_NIR (b) channels. Scatterplot (c) of corresponding available pixels in each image.
Fig 4.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images under high river discharge (> 66th percentile) over the period 2003–2015.
Results compare data obtained from Aqua (a) and Terra (b) satellites. Scatterplot (c) of corresponding pixels in each image.
Fig 5.
(a) Percentage of valid values, (b) mean value, and (c) standard deviation for each pixel of the composite considering all MODIS images under high river discharge (> 66th percentile) over the period 2003–2015.
Fig 6.
a) Correlation between the daily river discharge and the plume extension for different threshold values. The river discharge is presented for different delays respecting the date of sampling the turbid plume. Only daily images with more than 70% of available pixels covering the area of the sampled plume were utilized. The distribution of pixels for different threshold intervals are shown for images with (b) a negligible plume and (c) a well-developed plume.
Fig 7.
(a) Annual cycle variability of the Tagus River plume extension (km2) over the period of 2003 to 2015. Solid black line: monthly average; line inside each box: median; lower and upper whiskers: minimum and maximum, respectively; lower and upper box limits: first and third quartiles, respectively. Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images under (b) low river discharge (< 33th percentile) and (c) high river discharge (> 66th percentile) over the period 2003–2015. The black line represents the turbid threshold (0.2 mWcm-2μm-1sr-1).
Fig 8.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images under (a) northern and (b) southern alongshore winds over the period 2003–2015. Black line represents the turbid threshold (0.2 mWcm-2μm-1sr-1). (c) Map of differences on the Tagus turbid plume field under alongshore winds (southern minus northern winds).
Fig 9.
Transect of turbidity for alongshore winds for the (a) perpendicular and (b) parallel directions refer to ROFI coast (see Fig 1). Black line represents southern alongshore winds and grey line northern alongshore winds. Red line represents the turbid threshold. The zero marks the river mouth and negative distances refer to the region located northern to the river mouth.
Fig 10.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images under (a) eastern and (b) western cross-shore winds over the period 2003–2015. The black line represents the turbid threshold (0.2 mWcm-2μm-1sr-1). (c) Map of differences on the Tagus turbid plume field under cross-shore winds (western minus eastern winds).
Fig 11.
Transect of turbidity for cross-shore winds for the parallel direction refer to ROFI coast (see Fig 1).
Black line represents western cross-shore winds and grey line eastern cross-shore winds. Red line represents the turbid threshold. The zero marks the river mouth and negative distances refer to the region located northern to the river mouth.
Table 3.
Characteristics and implications of the Tagus turbid plume under wind forcing.
Fig 12.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images (a) before spring tides, (b) during and after spring tides, (c) before neap tides and (d) during and after neap tides, over the period 2003–2015. The black line represents the turbid threshold (0.2 mWcm-2μm-1sr-1).
Fig 13.
Mean water-leaving radiance (mWcm-2μm-1sr-1) composite at 645 nm for all MODIS images for (a, b) high and low tides during-after spring tides and (c, d) high and low tides during-after neap tides, over the period 2003–2015. The black line represents the turbid threshold (0.2 mWcm-2μm-1sr-1).
Table 4.
Characteristics and implications of the Tagus turbid plume under tidal forcing.
Table 5.
Dynamical parameters of the Tagus plume.