Structure perturbations in above-water radiometric measurements
The European Union’s Copernicus Earth Observation programme produces and delivers satellite data products to sustain the monitoring of the aquatic environment. Field radiometry allows to assess the accuracy of these data products and demonstrate that they meet users’ requirements. Because of this, over the last decades an increasing number of above-water autonomous systems have been deployed on offshore platforms to perform in situ radiometric measurements and contribute to such a validation task. The present work, aiming to support the quality assurance of these validation data, investigates the perturbing effect induced on above-water measurements by deployment structures —henceforth, structure perturbations (SP). The Acqua Alta Oceanographic Tower (AAOT) in the north Adriatic Sea is the case study selected for this investigation, which acknowledges former SP experimental studies and also the detailed characterisation of environmental properties at the site. The rationale of this work builds on the appreciation that a complete SP analysis only relying on in situ data would be limited by the difficulty to address the variety of potential measurement conditions. Conversely, Radiative Transfer (RT) simulations provide the capability to investigate any required field measurement setting and measurement condition. In this case study, simulation and experimental results show overall agreement, with differences partially explained by the difficulty to accurately set the reflective properties of each AAOT element. The results document the SP dependence on the measurement geometry, illumination conditions and reflective properties of the deployment structure. In addition to the distance between the deployment structure and the sensor footprint at the sea surface, a marked SP dependence on the sun zenith is also evidenced. The work additionally shows that SP on measurements performed with the AERONET-OC system hosted at AAOT is overall negligible when applying basic quality assurance criteria. These findings highlight how measurements taken with above-water systems deployed on oceanographic towers, as well as research vessels, would definitely benefit from SP analyses equivalent to that presented here for the AAOT.
D'ALIMONTE Davide;
BULGARELLI Barbara;
ZIBORDI Giuseppe;
KAJIYAMA Tamito;
2025-06-13
Publications Office of the European Union
JRC142107
978-92-68-28432-2 (online),
1831-9424 (online),
EUR 40346,
OP KJ-01-25-322-EN-N (online),
https://publications.jrc.ec.europa.eu/repository/handle/JRC142107,
10.2760/9773884 (online),
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