16:00–16:15 | ABSTRACT 1155
OBSERVATION OF SARGASSUM FROM A LONG-RANGE DRONE TO IMPROVE SATELLITE DETECTION AND DRIFT SIMULATIONS
Massive strandings of Sargassum have been occurring since 2011 on the coasts of the Caribbean and of West Africa, with major health, environmental and economic consequences. To mitigate these consequences, strandings are forecasted by detecting Sargassum aggregations in satellite imagery and simulating their drift and biological dynamics using models. However, field data are needed to validate and improve these forecasts but are scarce due to the difficulty and cost of collecting them. In May 2025, a long-range UAV (Unmanned Aerial Vehicle) was conducted with two objectives: to observe Sargassum synchronously with the Sentinel-3 satellite to improve detection algorithms, and to fly over Sargassum aggregations multiple times to acquire drift data to improve drift models. Nine flights were completed, seven of which lasted more than 6 hours and covered more than 500 km. Data were acquired with a multispectral camera. Several pre-processing steps were performed including radiometric corrections, band alignment, georeferencing and conversion to reflectance. Sargassum aggregations were detected based on the computation of the AFAI (Alternative Floating Algae Index) and then co-located with satellite detections. The largest rafts were then identified and tracked at different time intervals to determine their drift speed and direction. Preliminary results highlight variability in Sargassum density, with some areas completely free of Sargassum, while others exhibit high densities of rafts in windrows or large mats. The median drift direction and speed in the study area are approximately 310° and 0.8 m/s. Such data will be used to improve satellite detection and drift simulations.
Marianne Debue, CNRM (Météo-France / CNRS), [email protected]
Sarah Barbier, Météo-France, [email protected]
Etienne Blot, Météo-France, [email protected]
Warren Daniel, Météo-France, [email protected]
Michel Gavart, Boreal SAS, [email protected]
Florian Gibier, Météo-France, [email protected]
Thibault Guinaldo, Météo-France, [email protected]
Julien Metge, Boreal SAS, [email protected]
Stéphane Saux-Picart, Météo-France, [email protected]
Eric Vogel, Boreal SAS, [email protected]
