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纬向喷流形成和维持的动力学机制及其对大气混合和输送的影响的理解。该方法的基础是观察到势涡（PV）是一个基本的动力学量，可以统一小尺度涡旋混合、射流上的波传播以及由于波浪在其附近破碎而引起的混合等问题。特别是，该项目将解决：(i)角动量守恒（自然，因为纬向平均结构，如纬向射流包含大部分大气角动量）和流动稳定性引起的纬向射流的基本约束；㈡波浪动力学（以及相关的涡流动量通量）和临界水位的作用；在PV跳跃上传播的边缘波与在光滑背景PV梯度上传播的波的作用；（iii） PV混合作为纬向射流形成的途径，与能量梯级方向无关；（iv）示踪剂混合和运输以及射流作为运输屏障的作用；(v)射流演化与射流合并机制；（vi）二次环流和通过垂直运动形成陡峭的示踪梯度；示踪剂和PV梯度对准。所涉及的动力学过程控制着在陆地大气和海洋以及气态巨行星大气中观测到的地带性结构。这项工作将涉及气候科学的几个领域，包括中纬度风暴路径的变异性、亚热带急流和北极振荡、水文循环、平流层臭氧恢复、平流层和对流层的动力耦合、以及穿越温带对流层顶的运输和混合。