Response of a Mesoscale Dipole Eddy to the Passage of a Tropical Cyclone: A Case Study Using Satellite Observations and Numerical Modeling

Mesoscale eddies occurring in the world's oceans typically exist in pairs known as mesoscale dipole eddies or simply dipole eddies. Tropical cyclones (hereafter TCs) that move over the world's oceans often encounter and interact with these dipole eddies. Through this interaction, TCs induce significant perturbations in the mesoscale eddies. However, the specific influences that the passage of a TC on a dipole eddy have not been addressed. In this paper, a case study of the dipole eddy's response to the passage of a TC is conducted by using satellite observations and numerical simulation. The passage of a TC induces a long-duration response in the dipole eddy. First, the cyclonic ocean eddy component (COE) of the dipole is amplified, and the anticyclonic ocean eddy component (AOE) is weakened or even destroyed during the interaction. The amplification of the COE and weakening of the AOE primarily manifests as a change in their amplitudes and radii and as the adjustment of their vertical structure. The dipole eddy's response to the interaction with a TC manifests as an upwelling anomaly and the injection of positive relative vorticity. Following the passage of the TC, the COE gradually stabilizes, and AOE slowly recovers after the disturbance energy from the interaction dissipates, which facilitates the reestablishment of the dipole eddy. The dipole reaches an equilibrium state through a quasi-geostrophic adjustment process. As a consequence, the overall effect of the interaction of the dipole with the TC leads to an asymmetric signature on the dipole eddy. The eddy-eddy interaction in a dipole may allow it to stabilize in a shorter time relative to that of a solitary eddy.

Automated summary

When tropical cyclones pass over the world's oceans, they often interact with mesoscale dipole eddies, resulting in amplified cyclonic ocean eddy components and weakened or destroyed anticyclonic ocean eddy components. The interaction leads to changes in the amplitudes, radii, and vertical structures of the eddies, as well as the injection of positive relative vorticity and an upwelling anomaly. After the passage of the tropical cyclone, the dipole eddy gradually stabilizes and recovers through a quasi-geostrophic adjustment process, eventually reaching an equilibrium state.