Affiliation:
1. School of Marine Sciences, and Center for Ocean-Atmosphere Dynamical Studies, Nanjing University of Information Science and Technology, Nanjing, China
2. School of Marine Sciences, and School of Atmospheric Sciences, and Center for Ocean-Atmosphere Dynamical Studies, Nanjing University of Information Science and Technology, Nanjing, China
Abstract
AbstractThe internal dynamical processes underlying the Kuroshio large meander are investigated using a recently developed analysis tool, multiscale window transform (MWT), and the MWT-based canonical transfer theory. Oceanic fields are reconstructed on a low-frequency mean flow window, a mesoscale eddy window, and a high-frequency synoptic window with reference to the three typical path states south of Japan, that is, the typical large meander (tLM), nearshore non-large meander (nNLM), and offshore non-large meander (oNLM) path states. The interactions between the scale windows are quantitatively evaluated in terms of canonical transfer, which bears a Lie bracket form and conserves energy in the space of scale. In general, baroclinic (barotropic) instability is strengthened (weakened) during the tLM state. For the first time we found a spatially coherent inverse cascade of kinetic energy (KE) from the synoptic eddies to the slowly varying mean flow; it occupies the whole large meander region but exists only in the tLM state. By the time-varying multiscale energetics, a typical large meander is preceded by a strong influx of mesoscale eddy energy from upstream with a cyclonic eddy, which subsequently triggers a strong inverse KE cascade from the mesoscale window to the mean flow window to build up the KE reservoir for the meander. Synoptic frontal eddies are episodically intensified due to the baroclinic instability of the meander, but they immediately feed back to the mean flow window through inverse KE cascade. These results highlight the important role played by inverse KE cascades in generating and maintaining the Kuroshio large meander.
Funder
National Natural Science Foundation of China
National Program on Global Change and Air-Sea Interaction
Jiangsu Program of Entrepreneurship and Innovation Group
Jiangsu Chair Professorship
The Startup Foundation for Introducing Talent of NUIST
Natural Science Foundation of the Higher Education Institutions of Jiangsu Province
Publisher
American Meteorological Society
Cited by
14 articles.
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