The performance of the US Navy's RELO ensemble, NCOM, HYCOM during the period of GLAD at-sea experiment in the Gulf of Mexico

RELO ensembles have been applied to Lagrangian trajectory prediction, and it is demonstrated that either ensemble can provide valuable uncertainty information in addition to predicting the particle trajectory with highest probability in comparison with a single ocean model forecast. The calibrated ensemble with more reliability is able to capture some trajectories in different, even opposite directions which are missed by the un-calibrated ensemble. When the ensembles are applied to computing the LCS (Lagrangian Coherent Structure), the uncertainties of the LCSs, which cannot be estimated from a single model forecast, are identified. Another finding is that the LCS depends on the model resolution. The model with highest resolution produces the finest small-scale LCS structures, while the model with lowest resolution generates only large scale LCSs. The work on using ocean ensembles in Lagrangian ocean dynamics presented in this paper represents our initial attempt in this field. It is expected that this work will lead to more extensive new research in this area in the near future.