Towards a particle trajectory modelling approach in support of South African search and rescue operations at sea

The ability to provide rapid decision support and more precise search area coordinates for rescuers to conduct search and rescue operations at sea are of high impact value for marine and maritime stakeholders. Search and rescue operations rely on accurate information about metocean conditions to locate objects in the ocean. These include local knowledge, operational ocean and wind forecasts and empirical drift relationships between ocean currents, ocean surface winds and the objects being searched for. To provide more accurate decision support for rescuers looking for persons or objects lost at sea, a virtual particle tracking tool was combined with an empirical Leeway drift model. The Lagrangian Ocean Search Targets (LOST) application builds on a Lagrangian ocean analysis framework which has been adapted to provide real-time estimates of the positions of objects based on operational ocean and wind forecasts. LOST incorporates the impact of ocean currents, surface winds and stochastic motion, the latter being critical in accounting for sub-grid scale processes that are not resolved in the ocean and wind forecasts. This study assesses the accuracy of LOST, demonstrating its feasibility as a decision support tool for search and rescue operations by applying it to three use cases in the South African regional ocean. These use cases are real-life scenarios that highlight the value of combining state-of-the-art ocean and wind forecasting systems with Lagrangian ocean analyses frameworks and sub-grid scale parameterisation to support global operational oceanography.