海洋涡旋移动特征的区域划分方法及应用分析

为了合理有效地分析和挖掘海洋涡旋移动数据中的规律和模式,本文以基于空间交互性流聚类的区域化方法为基础,提出了一种海洋涡旋移动特征的网格区域化方法。该方法以网格为统计单元,对涡旋移动数据进行组织,通过图论模型构建海洋涡旋的移动网络图,然后采用基于平均邻接的层次聚类和基于模块度的划分2个步骤,实现涡旋移动特征的区域划分。基于该算法,对1992-2011年中国南海海洋涡旋移动数据进行算法实验,结果表明,南海海洋涡旋按照其移动频繁性特征可分为越南东南部（R1）、越南东部-巴拉望岛（R2）、南海北部（R3）3个区域。其中,R1区域包含了南海西南部深海盆地区的涡旋活跃条带;R2区域体现了南海中部涡旋向西移动的活动规律;R3区域则包含了南海北部东北-西南走向条带。3个区域内冷涡和暖涡具有明显的季节性变化特征：R1和R3区域冷暖涡变化相似,暖涡在夏秋季移动最多,冬季最少,而冷涡则相反,夏秋季移动最少,随后逐渐增加,并在春季达到峰值;R2区域暖涡在春季移动最多,而冷涡在夏冬移动最多,春秋移动相对较弱。

Regionalization Based on the Propagation of Ocean Eddies: Methods and Applications

Ocean eddy is a dynamic phenomenon which continuously propagates and evolves. In oceanography, eddy variability is always a hot topic. In previous studies, the results from different aspects such as the literature study, observation and simple mathematical statistics, are relatively general and subjective. Eddies' zonal aggregated propagation and regionalization, which classified a large set of spatial objects into several homogeneous spatially contiguous regions, can help the discovery of zonal flow patterns. This study introduces the regionalization method into investigating the zonal moving characteristics of ocean eddies. And we present a quantitative and systematic method, which is a spatially constrained regionalization method based on the propagation of ocean eddies on spatial grids to explore and discover the characteristics and laws of eddies' propagation. Firstly, we construct a weighted network of eddies′ propagation through refactoring the eddy moving characteristics on the grid basis (each grid is a spatial sea unit), and then employs the spatially constrained regionalization method to divide the network of eddies' propagation into spatial continuous sub-regions. The adjacency-based regionalization method includes two steps: first, it constructs a hierarchy of clusters, which is a spatially contiguous tree, from the bottom up by iteratively merging the most connected nodes in the weighted network; and then, the spatially contiguous tree is partitioned from the top down, by finding the best edge to remove. A case study has been carried out on the ocean eddies identified in the South China Sea (SCS) for a period between 1992 and 2011. Three major regions are discovered by the proposed method: southeast of Vietnam (R1), east of Vietnam-Palawan (R2), and north of SCS (R3). These three regions are consistent with the discovered active propagation laws of ocean eddies in SCS: R1 covers the active band of ocean eddies in the deep sea basin of the south-western SCS; R2 well reflects the westward moving pattern of eddies in the central SCS; and R3 covers the sea areas along the northeast-southwest continental slope in the northern SCS. These findings show that the spatially constrained regionalization is efficient and quantitative, which is an appropriate method to study the moving patterns of ocean eddies. Also, we analyze the seasonal variation of eddies′ propagation within and across the three regions. The results demonstrate that there are different seasonal variations in the warm and cold eddies for the three regions. And the seasonal variations of eddies′ propagation in R1 and R3 is roughly similar: the warm eddies′ propagation in both R1 and R3 reach its peak in summer and fall but diminishes significantly in winter, whereas the cold eddies′ propagation, on the contrary, is weak in summer and fall, but increases gradually in winter and reaches its peak in spring. In R2, the warm eddies' propagation is most intensive in spring while the cold eddies' propagation is strong in summer and winter but weak in spring and fall. In summary, this paper provides a new perspective and approach to explore and study propagation characteristics and laws of ocean eddy by introducing the spatially constrained regionalization method creatively.