The effects of vertical mixing on the transport of oil spills using the OpenDrift ocean trajectory model with ROMS/NorKyst800 forcing from May 5-11, 2011

New parameterizations for physical processes that are related to the vertical transport of oil spills are implemented into the open source trajectory framework OpenDrift. These encompass the wave-entrainment of oil, two alternative formulations for the droplet size spectra, and turbulent mixing. The performance of the integrated oil spill model is evaluated by comparing model simulations with airborne observations of an oil slick. The results show that an accurate description of a chain of physical processes – in particular vertical mixing and oil weathering – is needed to represent the horizontal spreading of the oil spill. Using ensemble of simulations of a hypothetic oil spill, the general drift behavior of an oil spill is discussed. Vertical mixing of oil between the surface slick and entrained oil is identified as a crucial component for the horizontal transport of oil spills, and to explain the differences for drift of various oil types.

针对与溢油垂直输运相关的物理过程，本研究为开源轨迹框架OpenDrift新增了参数化方案。该方案涵盖原油的波浪夹带效应、两种用于描述液滴尺寸谱的备选公式，以及湍流混合过程。通过将模型模拟结果与浮油的机载观测数据进行对比，我们对集成式溢油模型的性能进行了评估。研究结果显示，若要准确表征溢油的水平扩散过程，需对一系列物理过程——尤其是垂直混合与石油风化（oil weathering）——进行精准刻画。通过开展假设性溢油的集合模拟实验，本研究探讨了溢油的一般输运行为。研究证实，表层油膜与夹带原油之间的垂直混合，是影响溢油水平输运的关键环节，同时也可解释不同类型原油的输运差异。