基于客观λ_(2)方法的海洋三维涡旋核心线提取

Oceanic 3D vortex coreline extraction using the objectiveλ_(2)method

涡旋核心线是海洋中尺度涡旋结构的重要组成要素,涡旋核心线提取和可视化对于切入中尺度涡三维结构研究、开展海洋垂直物质能量运输分析具有重要意义。本文基于客观参考框架和λ_(2)准则,提出了使用客观化的流场参数得到λ_(2)区域,并提取其山谷线作为涡旋核心线的方法,实现了对海洋三维结构中尺度涡旋核心线的提取和可视化。首先,引入了最优局部参考系,使得速度、速度梯度等测度成为在变化的参考系下保持不变的客观量,提升了在海洋科学实践中的可靠性和实用性;其次,针对含有垂向速度的海洋三维流场数据,计算其空间雅可比矩阵,展示了涡旋核心区域的三维结构,实现了海洋涡旋研究从二维到三维的提升;最后,分别在多个半径大小播撒流线种子点,分析不同旋转方向的涡旋,对已提取的涡旋核心线实验结果进行验证,证明了客观λ_(2)海洋三维涡旋核心线提取方法的有效性及可行性。

Vortex corelines are an important component of the oceanic mesoscale eddy structure.The extraction and visualization of the vortex corelines are of great significance for the study of the three-dimensional structure of the mesoscale eddies and the analysis of the vertical oceanic material and energy transport.Based on the objective reference frame and theλ_(2)criterion,this paper proposes a method to obtain theλ_(2)region using the objective flow field parameters;and extract its valley line as the vortex coreline.First,the optimal local reference frame is introduced;so that measurements such as velocity and velocity gradient become objective quantities that remain unchanged under the changing reference frame,which improves the reliability and practicability of marine science practice.Secondly,for the three-dimensional ocean flow field data with vertical velocity,the spatial Jacobian matrix is calculated,which shows the three-dimensional structure of the vortex core region,and realizes the improvement of ocean vortex research from two-dimensional to three-dimensional.Finally,the experimental results of the extracted vortex corelines are verified by the analysis of vortexs in the different rotation directions and the different radius of streamline seed points,which proves the effectiveness and feasibility of the objectiveλ_(2)ocean three-dimensional vortex coreline extraction method.