Dear Colleagues and Students,

The State Key Laboratory of Internet of Things for Smart City would like to invite you to join our “IOTSC Talk Series” on 21/01/2025 (Tuesday). We are pleased to invite Prof. Zhiyu LIU from Xiamen University as the speaker.

On the Interactions and Energy Cascades of Multi-scale Oceanic Motions
Speaker: Prof. Zhiyu LIU
Date: 21/01/2025 (Tuesday)
Time: 15:00 – 16:00
Language: English
Venue: N21-5007 (Exhibition Hall)

Abstract:
The Earth’s ocean is a forced-dissipative system being operated at a wide range of spatiotemporal scales. In order to achieve quasi-equilibrium, the kinetic energy in the ocean transfers from scales of forcing at the basin scale to viscous dissipation at the molecular scale. This energy transfer process, covering nearly ten orders of magnitude, is called energy cascade. Oceanic energy cascade is a fundamental issue of physical oceanography and also a classic puzzle due to challenges in observations as well as in numerical and theoretical modeling. Processes at all these scales occur in the western Pacific Ocean, for example from the strong western boundary currents, vigorous mesoscale eddies and internal waves down to small-scale overturns; thus, it is an ideal experimental area for studies of oceanic energy cascade and multiscale interactions. Over the past five years, systematic studies on these topics were conducted via a combination of in-situ and remote sensing measurements, multiscale coupled numerical simulations, and theoretical analyses of ocean dynamics. Key findings/research outcomes include device of a dynamical decomposition of multi-scale oceanic motions, identification of the mechanism of tide-induced near-inertial waves (NIWs) and their interactions with wind-induced NIWs, and revealing mechanisms of the fission of shoaling internal solitary waves. With such research progress, we have gained a much better understanding of the interactions and energy cascades of multi-scale oceanic motions. Specifically, 1) by extending the dynamic theory of (un)balanced modes, we proposed a dynamical filter to decompose oceanic balanced and unbalanced motions, and obtained the decomposed physical fields and the corresponding governing equations for the two types of motions, thus establishing a new framework for quantifying the cross-scale interactions and associated energy transfers; 2) we identified a new mechanism of tide-induced NIWs, i.e., tidal forcing alone can generate a Garrett-Munk internal wave spectrum, and further elucidated the nonlinear interacting mechanisms controlling the mutual enhancement of wind- and tide-induced NIWs.

Speaker’s Bio:
Prof. Zhiyu Liu received his B.Sc. and Ph.D. from the Ocean University of China. Since 2015, he has been a professor at Xiamen University. He is dean of College of Ocean and Earth Sciences, Xiamen University and the associate director of State Key Laboratory of Marine Environmental Science (Xiamen University). He is also an Editor of the Journal of Oceanography, Ocean Dynamics and Geoscience Letters. Professor Liu’s research interests include ocean turbulence and mixing, geophysical instabilities, ocean scale interactions and energy transfers, internal gravity waves, upper ocean dynamics, wave-turbulence/vortex decomposition/interactions, water mass transformation and overturning circulation.

For enquiries: Tel: 8822 9159
Email: frankielei@um.edu.mo

Best Regards,
State Key Laboratory of Internet of Things for Smart City