基于拉格朗日拟序结构的黑潮区域海流运输结构提取和分析

Extracting and analyzing current transport structures in the Kuroshio area based on Lagrangian coherent structures

海流的拉格朗日运动对于研究物质输送有着重要意义,拉格朗日拟序结构(LCSs)作为研究海流结构的新型方法,相比于传统欧拉方法更为客观。本文提出了一种新的计算LCSs束的方法,基于25年的平均速度场,利用变分方法计算得到黑潮区域的气候态LCSs,并通过简化合并的方法得到了气候态LCSs束,该LCSs束能够突出地显示出海流特性和运输模式,其代表的平均拉格朗日环流有很强的约束作用,且具有鲁棒性。最终我们获得了气候态下12个月份的流场结构图,揭示了月周期性拉格朗日环流规律。本文还利用虚拟粒子输运、多年浮标轨迹以及气候态温盐异常3种方法进行了验证,与拉格朗日运输模式相吻合,证明了海流拉格朗日拟序结构的准确性和可靠性。

Lagrangian motion of fluid has important significance for studying material transport. Compared with the traditional Euler method, Lagrangian coherent structures(LCSs) as a new method to research current structures is more objective. This paper presents a new method to calculate LCSs bundles. Based on the average velocity fields of 25 years, climatological LCSs of the Kuroshio area are calculated by variational method. Then simplify and merge the LCSs to obtain climatological LCSs bundles. The LCSs bundles can show the typical current characteristics and transport patterns, represent the average Lagrangian circulation which has a strong constraint. Finally,the climatological flow structures for 12 months are obtained, revealing the periodic Lagrangian circulation rules in different months. Also, virtual particle transport, trajectories of drifters, temperature and salt anomalies distributions are used to verify the results, which are consistent with the transport patterns mentioned in this paper, proving the accuracy and reliability of the current Lagrangian coherent structures.