Articles | Volume 16, issue 8
Nat. Hazards Earth Syst. Sci., 16, 1979–1997, 2016

Special issue: Situational sea awareness technologies for maritime safety...

Nat. Hazards Earth Syst. Sci., 16, 1979–1997, 2016

Research article 29 Aug 2016

Research article | 29 Aug 2016

Evaluation of the search and rescue LEEWAY model in the Tyrrhenian Sea: a new point of view

Antonia Di Maio1, Mathew V. Martin2, and Roberto Sorgente3 Antonia Di Maio et al.
  • 1Marine Technology Research Institute INSEAN, National Research Council of Italy, Rome, Italy
  • 2Centre for Oceans, Rivers, Atmosphere and Land Sciences, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India
  • 3Institute for Coastal Marine Environment IAMC, National Research Council of Italy, Oristano, Italy

Abstract. The trajectories' prediction of floating objects above the sea surface represents an important task in search and rescue (SAR) operations. In this paper we show how it is possible to estimate the most probable search area by means of a stochastic model, schematizing the shape of the object appropriately and evaluating the forces acting on it. The LEEWAY model,a Monte Carlo-based ensemble trajectory model, has been used; here, both statistical law to calculate the leeway and an almost deterministic law inspired by the boundary layer theory have been considered. The model is nested within the subregional hydrodynamic model TSCRM (Tyrrhenian Sicily Channel Regional Model) developed in the framework of PON-TESSA (Programma Operativo Nazionale; National Operative Program – TEchnology for the Situational Sea Awareness) project. The main objective of the work is to validate a new approach of leeway calculation that relies on a real person in water (PIW) event, which occurred in the Tyrrhenian Sea in July 2013. The results show that by assimilating a human body to a cylinder and estimating both the transition from laminar to turbulent boundary layer and the drag coefficients, it can be possible to solve a force balance equation, which allows the search area to be estimated with good approximation. This new point of view leads to the possibility of also testing the same approach for other different categories of targets, so as to overcome the limitations associated with the calculation of the leeway in the future by means of standard statistical law.

Short summary
Meteocean and environmental forecasting is increasingly being used in operational decision-making in the sea for demographic, geographic and strategic applications. It also used to force the stochastic models used for search and rescue planning. The stochastic models have many limitations relating to the leeway calculation, and we tried to overcome them; we hope to contribute by providing leeway drift formulae for practical use.
Final-revised paper