Water properties in the La Plata River Estuary from VIIRS observations

In this study, observations from the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) between 2012 and 2018 are used to characterize and quantify water optical properties in the La Plata River Estuary (or Rio de la Plata Estuary). Satellite-measured normalized waterleaving radiance spectra nL(w)(lambda) are found to be similar with the peak at the 671 nm red band in the inner and mid estuaries, while nL(w)(lambda)) spectra peak at the 551 nm green band in the outer estuary. Remarkable seasonal and inter-annual variability are also observed in the La Plata River Estuary. The austral autumn (March-May) is found to be the most turbid season. An enhanced radiance ratio nL(w)(745)/nL(w)(671) is also found to occur during the austral autumn season in the inner and mid estuaries. The La Plata River Estuary had the most turbid water in 2012 in terms of the satellite-measured water diffuse attenuation coefficient at 490 nm K-d (490) in the inner and mid estuaries. The low K-d (490) in the inner and mid estuaries during 2015-2016 coincided with the strong 2015-2016 El Nino event. The first and second empirical orthogonal function (EOF) modes account for about 34.9% and 27.0% of the total K-d (490) variance in the La Plata River Estuary, respectively. In addition, the K-d (490) variation in the inner and mid estuaries is out of phase with that in the outer estuary. The winds, rainfall, and river discharge are attributed to the first and second EOF modes of the K-d(490) in the La Plata River Estuary.