报告题目：Asymmetrical response of flow in a shelf valley to along-shelf winds of opposite directions
内容提要：This study investigates the mechanism of the asymmetrical valley flow response to along-shelf winds of opposite directions. Simulations demonstrate that: i) when the wind is in the same direction as coastal-trapped wave (CTW) phase propagation, the flow forms a symmetric onshore detour pattern over the valley with negligible down-valley transport (downwelling regime); and ii) when wind is in the opposite direction as CTW propagation, the shelf flow turns onshore in the valley and generates strong up-valley transport (upwelling regime) and a standing meander on the upstream side of the valley (in the sense of CTW phase propagation). This work reveals that the up-valley flow in the second scenario results from CTWs being arrested by the wind-driven shelf flow establishing lee waves. The valley bathymetry generates an initial excessive onshore pressure gradient force, drives the up-valley flow, and induces CTW lee-waves that sustain the up-valley flow. When the wind-driven shelf flow aligns with CTW phase propagation, the initial disturbance generated in the valley propagates away, and the valley flow adjusts to roughly follow isobaths. This mechanism of arrested CTWs generating stronger onshore than offshore flow is expected to be applicable to the response of slope canyons to along-isobath background flows of opposite directions.
主讲人：Weifeng (Gordon) Zhang, Woods Hole Oceanographic Institution
主讲人简介：Weifeng (Gordon) Zhang, Associate Scientist at Woods Hole Oceanographic Institution. His research focuses on physical and biological processes in coastal oceans, including interactions of coastal flow features with topography and with processes in estuaries and the open ocean. He combines numerical models with observational analysis to improve the understanding of coastal ocean systems and the effect of natural and anthropogenic forces on the coastal environments that are directly connected to the well-being of our society. His research interests cover a broad range of topics in oceanography, including: coastal ocean circulation, frontal dynamics, internal wave dynamics, polynya circulation, gravity currents, data assimilation, model-based observing system design, and biophysical interactions.