Field Work for assessment of the leeway of drifting objects
Christophe Maisondieu, O. Breivik, A.A. Allen, J-C. Roth, M. Pavec
IFREMER
(Abstract received 07/10/2009 for session E)
ABSTRACT
Operational drift forecast models developed for prediction of the trajectory of objects lost at sea are now mostly based on stochastic approaches for the definition of search areas from computation of probable trajectories. Such models take into account environmental forcing components, mainly surface or near-surface currents and wind, as well as simplified drift speed computation models based on objects hydrodynamic and aerodynamic properties. Drifting properties of objects can be described by mean and standard error of their leeway coefficients. Assessment of these coefficients is based on a direct method which requires measurements acquired during field tests. We discuss here procedures for conducting such field tests and present results from campaigns for evaluation of leeway coefficients of various objects. Finally we present results of a drift forecast model for the case of a twenty-foot shipping container and discuss sensitivity of the forecast to quality of environmental data, by comparing results obtained using model data with results obtained with HF radar data. We also discuss the need to provide more sophisticated Lagrangian uncertainty estimates, models and parameters into operational Search and Rescue trajectory models.
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