The Potential Vorticity Staircase: Formation and Maintenance of Zonal Jets

势涡阶梯：纬向急流的形成和维持

• 批准号: 0827210
• 负责人: Richard Scott
• 金额: $ 51.96万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0827210&HistoricalAwards=false
• 关键词: Potential; Vorticity; Staircase; Formation; Maintenance

This project seeks to improve our understanding of dynamical mechanisms responsible for the formation and maintenance of zonal jets and their implications for atmospheric mixing and transport. The approach is underpinned by the observation that potential vorticity (PV) is a fundamental dynamical quantity that can unify questions of small-scale eddy mixing, wave propagation on jets, and mixing due to wave breaking in their vicinity. In particular, the project will address: (i) fundamental constraints on zonal jets arising from angular momentum conservation (natural, since zonal mean structures such as zonal jets contain most of the atmosphere's angular momentum) and flow stability; (ii) wave dynamics (and associated eddy momentum fluxes) and the role of critical levels; the role also of edge waves propagating on a PV jump in contrast to waves propagating on a smooth background PV gradient; (iii) PV mixing as a route to zonal jet formation, independently of the direction of energy cascade; (iv) tracer mixing and transport and the role of jets as transport barriers; (v) jet evolution and mechanisms of jet merger; (vi) secondary circulations and the development of steep tracer gradients through vertical motions; alignment of tracer and PV gradients. The dynamical processes involved govern zonal structures observed in the terrestrial atmosphere and oceans as well as in the atmospheres of the gas giants. The work will impinge on several areas of climate science, including variability of the mid-latitude storm tracks, subtropical jet, and Arctic oscillation, the hydrological cycle, stratospheric ozone recovery, the dynamical coupling of the stratosphere and troposphere, and transport and mixing across the extratropical tropopause.

该项目旨在提高我们对负责形成和维持纬向喷气机及其对大气混合和运输的影响的动态机制的理解。这种方法的基础是，观察到潜在的涡度（PV）是一种基本的动力学数量，可以统一小规模涡流混合，喷射波的波传播以及由于其附近的波浪破裂而引起的混合。特别是，该项目将解决：（i）由角动量保存产生的针对区域喷射的基本限制（自然，因为区域平均结构（例如Zonal Jets）包含大部分大气的角度动量）和流动稳定性； （ii）波动力学（以及相关的涡流通量）和临界水平的作用；与在光滑背景PV梯度上传播的波相反，边缘波在PV跳跃中的作用也是如此； （iii）PV混合作为通往纬向射流形成的途径，与能量级联方向无关； （iv）示踪剂混合和运输以及喷气机作为运输屏障的作用； （v）喷气合并的喷气演化和机制； （vi）二次循环和通过垂直运动的陡峭示踪梯度的发展；示踪剂和PV梯度的比对。动态过程涉及控制在陆地大气和海洋以及气体巨头大气中观察到的区域结构。这项工作将影响气候科学的多个领域，包括中纬度风暴轨迹的变化，亚热带射流和北极振荡，水文循环，平流层臭氧回收，平流层和对流层的动态耦合以及跨热地热带的运输和混合。