EddyGraph: The Tracking of Mesoscale Eddy Splitting and Merging Events in the Northwest Pacific Ocean

Abstract

This paper proposes an algorithm named EddyGraph for tracking mesoscale eddy splitting and merging events. Twenty-seven years (January 1993–December 2019) of sea level anomaly (SLA) data are analyzed in the Northwest Pacific Ocean (105°E–165°W, 0°N–60°N). First, we propose a multilevel eddy identification method based on SLA to obtain an eddytree data set, representing a spatial topological tree structure of closed SLA contours with mononuclear eddies, multicore eddies and eddy seeds as the leaf nodes and eddygroups (reflecting the spatial topological relationship among eddies) as the intermediate nodes. The EddyGraph tracking algorithm is applied to the eddytree data set, which results in eddy-directed acyclic graphs (Eddy-DAGs). Only eddies contained within a common eddygroup are tracked as sources in merging events or sinks in splitting events. Furthermore, we extract typical splitting and merging events and composite the sea surface temperature anomalies (SSTAs) inside the eddygroups and eddies during these events. The results confirm that merging eddies in the same eddygroup degenerate into a single eddy and that a splitting eddy evolves into eddies within the same parent eddygroup. Moreover, we match a merging event of cyclonic eddies with in situ data of both drifters and loopers in Lagrangian trajectories. Finally, we present EddyGraph, a data set of mesoscale eddy tracking in the Northwest Pacific Ocean (105°E–165°W, 0°N–60°N).

Lakshadweep High Propagation and Impacts on the Somali Current and Eddies During the Southwest Monsoon

“…This provides another way for the half and local LHs to diminish by transferring energy from the mesoscale to the submesoscale. Algorithms specifically tailored to the splitting and merging of eddies, e.g., Tian et al.’s (2021) EddyGraph , are currently being developed and may be used to more specifically quantify the effects of these processes on the LH. Additional submesoscale measurements, such as those collected from the NASA Surface Water and Ocean Topography (SWOT) mission, will also help elucidate this process of energy transfer.…”

“…These include the effect of eddy killing throughout the AS, the effects of submesoscale energy transfer via eddy splitting/merging events in the AS, and the variability of these factors by monsoon. When these questions and those following them are answered, whether by further investigation using existing techniques (e.g., Rai et al., 2021), new algorithms (e.g., Tian et al., 2021), and/or improved observations, such as from the upcoming National Aeronautics and Space Administration (NASA) SWOT mission, we will understand the LH phenomenon.…”

Quantifying the Degree of Eddy Quasi‐Geostrophy by Generalizing Rossby Deformation

“…To enhance our understanding of the significance of the proposed eddy QG index in eddy dynamic research, we conduct a case study on the variation of the index during an eddy merging/splitting event, as presented in Figure 7. Eddy merging and splitting are frequently observed complex dynamical processes in the ocean (e.g., Li et al, 2016;Tian et al, 2021;H. Wang et al, 2019).…”

“…To enhance our understanding of the significance of the proposed eddy QG index in eddy dynamic research, we conduct a case study on the variation of the index during an eddy merging/splitting event, as presented in Figure 7. Eddy merging and splitting are frequently observed complex dynamical processes in the ocean (e.g., Li et al., 2016; Tian et al., 2021; H. Wang et al., 2019). Figures 7a–7c display three snapshots of eddies during April 1–21, 1997, which exhibit simultaneous occurrences of eddy merging and splitting (marked with purple and dark blue boxes as A1 and A2, respectively), as also reported by Li et al.…”