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arXiv 2008.12253physics.ao-phphysics.flu-dyn
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轨迹聚类的不确定性量化在海洋环境预报中的应用

Uncertainty Quantification of Trajectory Clustering Applied to Ocean Ensemble Forecasts

Guilherme S. Vieira, Irina I. Rypina, Michael R. Allshouse

摘要:

基于物质运输将海洋流动划分为动态地不同于其周围环境的区域可以通过减少搜索域来帮助搜索和救援规划。谱聚类方法通过识别相似的流体粒子轨迹来划分域。分割的有效性取决于海洋预报的准确性,这是受几个来源的不确定性:模型初始化,有限的知识的物理过程,边界条件和强迫项。代替单个模型输出,产生跨越一系列潜在结果的多个实现,并且使用轨迹聚类来识别鲁棒特征并量化整体平均结果的不确定性。首先,利用集合统计量研究了一个地转流模式--解析Bickley急流的谱聚类方法自由参数和预报参数对聚类的敏感性。然后,我们分析了一个业务的沿海海洋集合预报和比较的聚类结果南玛莎葡萄园岛的漂流轨迹。这种方法准确地识别出低不确定性区域,其中在集群内释放的漂移物在整个分析窗口中保持在那里。在高不确定性区域释放的漂移物往往要么进入邻近的集群,要么偏离所有预测的结果。

英文摘要:

Partitioning ocean flows into regions dynamically distinct from their surroundings based on material transport can assist search-and-rescue planning by reducing the search domain. The spectral clustering method partitions the domain by identifying fluid particle trajectories that are similar. The partitioning validity depends on the accuracy of the ocean forecasting, which is subject to several sources of uncertainty: model initialization, limited knowledge of the physical processes, boundary conditions, and forcing terms. Instead of a single model output, multiple realizations are produced spanning a range of potential outcomes, and trajectory clustering is used to identify robust features and quantify the uncertainty of the ensemble-averaged results. First, ensemble statistics are used to investigate the cluster sensitivity to the spectral clustering method free-parameters and the forecast parameters for the analytic Bickley jet, a geostrophic flow model. Then, we analyze an operational coastal ocean ensemble forecast and compare the clustering results to drifter trajectories south of Martha's Vineyard. This approach accurately identifies regions of low uncertainty where drifters released within a cluster remain there throughout the window of analysis. Drifters released in regions of high uncertainty tend to either enter neighboring clusters or deviate from all predicted outcomes.

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