Strength and Spatial Structure of the Perturbation Induced by a Tropical Cyclone to the Underlying Eddies
Zhumin Lu, Guihua Wang, Xiaodong Shang
Abstract
Abstract A tropical cyclone (TC) induces the oceanic geostrophic response, which perturbs the underlying ocean eddy field. This study investigates the strength and spatial structure of isopycnal undulations and potential vorticity (PV) changes linked with the geostrophic response by use of a linear, two‐layer theory and an OGCM. It is found that the strength and cross‐track length scale of the geostrophic response are well compared with those of background eddies, highlighting the ability of a TC to perturb underlying ocean eddies. More importantly, the TC‐induced PV perturbation is confined within the thermocline between 100 and 300 m depth, causing the 3D quasi‐geostrophic evolution of the perturbed eddies. The length scale of upwelling perturbation (which is ~130 km) is larger than that of PV response (~50 km). This scale disparity means that the patterns of the TC‐induced perturbations are subject to eddy‐TC separation distance. Consequently, the perturbation of a TC to an eddy is significant (negligible) when the eddy‐TC separation distance is less than 80 km (larger than 200 km). This study provides a starting point for understanding the TC‐induced 3D evolution of the perturbed ocean eddy field.