Backtracking drifting objects using surface currents from high-frequency (HF) radar technology

Abstract

In this work, the benefits of high-frequency (HF) radar ocean observation technology for backtracking drifting objects are analysed. The HF radar performance is evaluated by comparison of trajectories between drifter buoys versus numerical simulations using a Lagrangian trajectory model. High-resolution currents measured by a coastal HF radar network combined with atmospheric fields provided by numerical models are used to backtrack the trajectory of two dataset of surface-drifting buoys: group I (with drogue) and group II (without drogue). A methodology based on optimization methods is applied to estimate the uncertainty in the trajectory simulations and to optimize the search area of the backtracked positions. The results show that, to backtrack the trajectory of the buoys in group II, both currents and wind fields were required. However, wind fields could be practically discarded when simulating the trajectories of group I. In this case, the optimal backtracked trajectories were obtained using only HF radar currents as forcing. Based on the radar availability data, two periods ranging between 8 and 10 h were selected to backtrack the buoy trajectories. The root mean squared error (RMSE) was found to be 1.01 km for group I and 0.82 km for group II. Taking into account these values, a search area was calculated using circles of RMSE radii, obtaining 3.2 and 2.11 km 2 for groups I and II, respectively. These results show the positive contribution of HF radar currents for backtracking drifting objects and demonstrate that these data combined with atmospheric models are of value to perform backtracking analysis of drifting objects.

Operational protocol for the sighting and tracking of Portuguese man-of-war in the southeastern Bay of Biscay: Observations and modeling

“…For surface drifters such as the tags analyzed here, this percentage is lower than the typical 3% value used in the drift of oil spills (Fallah and Stark, 1976;Wu, 1983). On average, 1.8% of the wind velocity is an optimal value that agrees with those obtained by Abascal et al (2009Abascal et al ( , 2012 with surface drifting buoys. Our results also reveal the importance of errors in wind forecasts.…”

“…In another paper, Abascal et al (2012) demonstrated that HF radar currents combined with modeled winds are of value for the backtracking of floating objects. Their results suggest that under calm wind conditions HF radar currents could be used as a unique forcing to simulate the trajectories of surface drifting buoys with a small drogue ($ 60 cm).…”

“…More information about the characteristics of this layer can be found in Ekman (1905). In the Bay of Biscay and in the northwestern coastal area of Spain, Sotillo et al (2008) and Abascal et al (2009Abascal et al ( , 2012 analyzed buoy trajectories and compared them with simulated trajectories. For their simulations, they used a combination of outputs from numerical models (wind, waves and ocean currents) and HF radar data.…”

Validation of high-frequency radar ocean surface current observations in the NW of the Iberian Peninsula

“…Previous researches have proved the positive contribution of HF radar current estimates for oil spill modeling (Ullman et al, 2006), trajectory analysis of floating objects (Abascal et al, 2009), back drift estimation techniques (Abascal et al, 2012), maritime Search and Rescue operations (Ullman et al, 2003;O'Donnell et al, 2005), assimilation into numerical circulation models (Oke et al, 2002;Paduan and Shulman, 2004;Gopalakrishnan and Blumberg, 2012) or the calibration and validation of operational ocean forecasting systems (Johnson et al, 2007;Hernández et al, 2009).…”

Application of a lagrangian transport model to organo-mineral aggregates within the Nazaré canyon

“…The application of lagrangian transport models linked to hydrodynamic models has a high potential to predict various environmental scenarios. At the western Iberian margin, lagrangian transport models have been applied to the Galician coast (Carracedo et al, 2006), Ria de Vigo (Huhn et al, 2012;Abascal et al, 2012), Rio Lima estuary (Vale and Dias, 2011), Ria de Aveiro lagoon (Dias et al, 2001),Óbidos lagoon (Malhadas et al, 2009) and Tagus estuary (Braunschweig et al, 2003). The operational model MOHID-PCOMS (MOdelação HIDrodinâmica Portuguese Coast Operational Modelling System) runs in full operational mode for the western Iberian coast with daily hydrodynamic and ecological results.…”