Assessment of a Lagrangian model using trajectories of oceanographic drifters and fishing devices in the Tropical Atlantic Ocean

Abstract

In the Tropical Atlantic Ocean, we assessed the accuracy of a Lagrangian model (Ichthyop) forced with velocity fields from a hydrodynamical model (CROCO) and two different remote sensing products (GlobCurrent and OSCAR) using trajectories of oceanographic drifters. Additionally, we evaluated the possibility to expand the drifters data using trajectories of GPS-buoy equipped drifting Fish Aggregating Devices (FADs). Tehe observed and simulated trajectories were compared in terms of spatial distribution, velocity distribution and a nondimensional skill score. For the drifters and FADs, the GlobCurrent and OSCAR products lead to similar performances as the CROCO model-ouputs in the broad studied domain. In the Gulf of Guinea, however, the CROCO model performed significantly better than the other two because the parent solution of CROCO benefited from its communication with a child grid of finer resolution in this region. On average, the simulations lead to an underestimation of the drifter and FAD velocities, likely because the spatial resolutions of the forcing products were insufficient and the time frequency at which they were produced were too low to resolve the relevant oceanic processes properly. We found a low skill for all models to simulate FAD trajectories, possibly because of the devices vertical structure that prevent FADs from drifting like water parcels. Our results therefore suggest that in the Tropical Atlantic the FAD dataset may not be appropriate to use for corroborating Lagrangian simulations. Highlights► Assessement of the accuracy of a Lagrangian model forced with different velocity fields using drifters and Fish Aggregating Devices (FADs). ► CROCO, OSCAR and GlobCurrent have the same performance. ► CROCO is better in the Gulf of Guinea than the satellite derived currents. ► The simulations underestimate the drifters and FADs velocities. ► FADs may not be appropriate to use for corroborating Lagrangian simulations.

The Impact of Ocean‐Wave Coupling on the Upper Ocean Circulation During Storm Events

“…However, it is not clear yet how to properly include this process when simulating drifter trajectories (e.g., Breivik & Allen, 2008; Callies et al., 2017; De Dominicis et al., 2016; Röhrs et al., 2012; Staneva et al., 2021; Sutherland et al., 2020). In addition, studies on modeling the trajectory of SVP drifters are scarce (e.g., Abascal et al., 2012; Amemou et al., 2020; Kjellsson & Doos, 2012), especially during storm conditions. Therefore the aim of this section is to assess the skills and the realism of our Lagrangian modeling approach.…”

“…Results are presented in terms of average skill scores and standard deviation SD, similarly to the studies of Amemou et al. (2020); Staneva et al. (2021); Tamtare et al.…”

“…Sensitivity tests using 1,000 or 10,000 particles showed no effect on the numerical solution. Results are presented in terms of average skill scores ss and standard deviation SD, similarly to the studies of Amemou et al (2020); Staneva et al (2021); Tamtare et al (2021).…”

“…et al, 2016;Röhrs et al, 2012;Staneva et al, 2021;Sutherland et al, 2020). In addition, studies on modeling the trajectory of SVP drifters are scarce (e.g., Abascal et al, 2012;Amemou et al, 2020;Kjellsson & Doos, 2012), especially during storm conditions. Therefore the aim of this section is to assess the skills and the realism of our Lagrangian modeling approach.…”

Spreading of Lagrangian Particles in the Black Sea: A Comparison between Drifters and a High-Resolution Ocean Model

“…The Ichthyop model was recently used in the BS to simulate distribution and accumulation of floating marine debris [41]. Our model only considers the physical flow field generated by the CROCO model by omitting the biological parameters on ichthyoplankton dynamics [40][41][42]. In this study, we used the Lagrangian model to launch virtual drifter trajectories computed at each time step using a Runge-Kutta 4 forward scheme.…”