Destruction of Potential Vorticity By Winds at Separated Western Boundary Currents

在分离的西部边界流上风对位涡的破坏本项目将利用高分辨率、面向过程的数值模拟，研究风对位涡(PV)的破坏在大气环流的两个关键要素：分离的西部边界流(SWBC)及其南部再循环涡旋(SRGs)的动力学中的作用。控制SRGS的物理机制与涡旋PV通量和产生低PV模式水的过程密切相关。定标论证和初步数值实验表明，与沿SWBC密度锋面吹来的风相关的摩擦力在形成低PV水方面与涉及与大气冷却相关的非绝热过程的经典机制一样有效。初步实验还表明，风生锋面上的涡旋涡旋通量通过地面摩擦涡旋通量随风应力的变化而变化。两种模型构型将用于拟议的数值试验。第一部分将集中在风力强迫的SWBC的锋面区域，以表征涡旋PV通量，并基于地面PV通量发展这些通量的参数化。另一种模型配置将包括一个双风回旋，带有倾斜的西边边界。这种配置是为了研究涡旋PV通量(由地面PV通量驱动)、涡旋尺度平流PV通量和底部Ekman层摩擦PV通量在决定SRG的PV和环流中的竞争效应。

Destruction of potential vorticity by winds at separated western boundary currentsThis project will investigate, using high-resolution, process-oriented numerical simulations, the role of destruction of potential vorticity (PV) by winds in the dynamics of two key elements of the general circulation: separated western boundary currents (SWBCs) and their southern recirculation gyres (SRGs). The physics governing SRGs is intimately tied to eddy PV fluxes and to the processes that create the low-PV mode water that fills the gyres.Scaling arguments and preliminary numerical experiments suggest that frictional forces associated with winds blowing along the density front of a SWBC can be as effective in forming low PV water, as the classical mechanism involving diabatic processes associated with atmospheric cooling. The preliminary experiments also suggest that eddy PV fluxes at wind-driven fronts scale with the wind-stress through the surface frictional PV flux. Two model configurations will be used for the proposed numerical experiments. The first will focus on the frontal region of a wind-forced SWBC to characterize the eddy PV fluxes and develop a parameterization for these fluxes based on surface PV fluxes. The other model configuration will consist of a double-wind gyre, with a sloping western boundary. This configuration is designed to study the competing effects of eddy PV fluxes (driven by surface PV fluxes), gyre-scale advective PV fluxes, and frictional PV fluxes in the bottom Ekman layer in determining the PV and circulation of the SRG.