Beron-Vera Francisco J, Olascoaga María J, Haller George, Farazmand Mohammad, Triñanes Joaquín, Wang Yan
Department of Atmospheric Sciences, RSMAS, University of Miami, Miami, Florida 33149, USA.
Department of Ocean Sciences, RSMAS, University of Miami, Miami, Florida 33149, USA.
Chaos. 2015 Aug;25(8):087412. doi: 10.1063/1.4928693.
Recent developments in dynamical systems theory have revealed long-lived and coherent Lagrangian (i.e., material) eddies in incompressible, satellite-derived surface ocean velocity fields. Paradoxically, observed drifting buoys and floating matter tend to create dissipative-looking patterns near oceanic eddies, which appear to be inconsistent with the conservative fluid particle patterns created by coherent Lagrangian eddies. Here, we show that inclusion of inertial effects (i.e., those produced by the buoyancy and size finiteness of an object) in a rotating two-dimensional incompressible flow context resolves this paradox. Specifically, we obtain that anticyclonic coherent Lagrangian eddies attract (repel) negatively (positively) buoyant finite-size particles, while cyclonic coherent Lagrangian eddies attract (repel) positively (negatively) buoyant finite-size particles. We show how these results explain dissipative-looking satellite-tracked surface drifter and subsurface float trajectories, as well as satellite-derived Sargassum distributions.
动力系统理论的最新进展揭示了在不可压缩的、源自卫星观测的表层海洋速度场中存在寿命长且连贯的拉格朗日（即物质）涡旋。矛盾的是，观测到的漂流浮标和漂浮物往往在海洋涡旋附近形成类似耗散的模式，这似乎与连贯拉格朗日涡旋产生的保守流体粒子模式不一致。在此，我们表明，在旋转二维不可压缩流的背景下考虑惯性效应（即由物体的浮力和有限尺寸产生的效应）可解决这一矛盾。具体而言，我们发现反气旋连贯拉格朗日涡旋吸引（排斥）负（正）浮力的有限尺寸粒子，而气旋连贯拉格朗日涡旋吸引（排斥）正（负）浮力的有限尺寸粒子。我们展示了这些结果如何解释类似耗散的卫星跟踪表层漂流器和次表层漂浮物轨迹，以及源自卫星观测的马尾藻分布情况。
