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105/11/15 14:00 臺灣大學海洋研究所陳世楠副教授 演講
演講公告
張貼人：網站管理員 ╱ 公告日期：2016-11-08演 講 公 告
主講人：陳世楠 副教授
地點：中央大學科學一館S-325教室
摘要：
講題：Stability of bottom-attached, buoyant coastal currents
主講人：陳世楠 副教授
臺灣大學海洋研究所
時間：11月15日（星期二）下午2點
地點：中央大學科學一館S-325教室
摘要：
Numerical experiments using a three-dimensional, primitive equation ocean model (ROMS) reveal that a range of idealized, bottom-attached, buoyant coastal currents fed by coastal discharge deviate strongly from the cross-shore geostrophic balance. In the body of propagating coastal currents, a wave-like feature of alternating cross-shore flow develops, with current speed of O(10 cm/s) and an along-shore wave spacing of a few baroclinic deformation radii. Increasing coastal discharge and decreasing density anomaly (i.e. reduced gravity) strengthen the cross-shore flow such that the coastal currents eventually become unstable. The classic Eady model, modified to account for the effects of a bottom slope (e.g. Blumsack and Gierasch (1972), is then used to evaluate whether the development of alternating cross-shore flow is a result of growing baroclinic instability. Preliminary analyses are supportive for this hypothesis: cases with large discharge and small reduced gravity generally lie near regions of large linearly growth rate in the stability diagram. The key parameter of this problem is the ratio of bottom slope to isopycnal slope. Decreasing discharge and increasing density anomaly flatten the isopycnal, meaning that there is less available potential energy (APE) to be extracted by the disturbance and thereby tending to stabilize the coastal currents. Moreover, for the unstable cases, the cross-shore velocity is intensified at two vertical boundaries and shows upstream phase tilt with height, generally in accord with the vertical structure of mutually reinforced Eady waves. Typical time scale for the development of alternating cross-shore flow is around 8 to 15 days, implying that these features are observable in the field. In this presentation, energy transfer between the base flow and wave field will be quantified.
最後修改時間：2016-10-31 AM 9:32
