Abstract
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.
Highlights
Meteocean and environmental forecasting is increasingly being used in operational decision-making in the sea for demographic, geographic and strategic applications
The LEEWAY model is used to reproduce a real event that occurred in the western Tyrrhenian Sea, along the coast of Sardinia
The distance between the mass center of each planting group and the retrieval point/time is shown in Fig. 4: we verify that the third group, planted between the 21:30 and 22:00 UTC, is the closest to the target, with a distance which oscillates around the value of 9 km; the smallest absolute distance is reached by the fourth group, planted between 22:00 and 22:30 UTC, 31.5 h later than the retrieval time
Summary
Meteocean and environmental forecasting is increasingly being used in operational decision-making in the sea for demographic, geographic and strategic applications. Having an efficient ocean forecast system is essential to improve the prediction of sea state and to provide useful environmental ocean information, so as to increase the effectiveness of search operations (Breivik et al, 2013). In the event of an accident, timely search and rescue (SAR) intervention is helpful in significantly lowering the loss of lives and to contain the damage. The effectiveness of the available SAR capabilities can be increased if we take advantage of high-quality environmental forecast data for SAR planning. An example of operational ocean forecasting and services coupled with search and rescue (SAR) activities is represented by the Global Ocean Data Assimilation Experiment (GODAE BLUElink) operational ocean prediction system (Brassington et al, 2007), used by the Australian Maritime Safety Authority. A list of global and regional operational ocean forecasting systems, supported by GODAE (Bell et al, 2009), can be found in Davidson et al (2009), while a recent review of the evolution of the global and regional forecasting system from GODAE into GODAE OceanView (Bell et al, 2015) is described in Tonani et al
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