Sensitivity analysis of wind drift parameter for lagrangian particle model of dummy drift trajectory in the Northern South China Sea

Abstract

In this study, we applied the Lagrangian particle model to simulate the drift trajectories of horizontal dummies in maritime environments, with a specific focus on the northern South China Sea. Wind exerts a force on floating objects, causing them to drift in a direction influenced by the wind direction and strength. The wind drift factor quantifies this effect, indicating how much the wind's force contributes to the overall drift velocity. Sensitivity analysis, employing both the one-at-a-time and Sobol methods, was conducted to examine the model's responses to variations in wind drift parameters. The findings underscore a significant impact of the wind drift factor on the drift trajectory, where an increase in the wind drift coefficient resulted in a gradual deviation of the drift point towards the left, and the overall drift trajectory deviated towards the west. Specifically, when the wind drift coefficient was varied, the model exhibited significant changes in the average drift trajectory and increased instability, as indicated by larger standard deviations. Variations in the depth of wind influence, which pertains to the vertical extent of wind effect on sea surface dynamics, had a relatively smaller impact on the model's output compared to changes in the wind drift factor. These results were further validated by comparing the LPM-simulated trajectories with those predicted by the National Maritime Search and Rescue System. The optimal sea surface wind drift factor, determined through sensitivity experiments, was found to be 0.016, which yielded the most precise simulation of the dummy's drift trajectory.