The Potential Vorticity Staircase: Formation and Maintenance of Zonal Jets

该项目旨在增进我们对纬向急流形成和维持的动力机制及其对大气混合和输送的影响的理解。这种方法的基础是，位涡(PV)是一个基本的动力学量，它可以统一小尺度涡旋混合、喷流上的波传播和附近的波破裂引起的混合问题。具体而言，该项目将涉及：(1)角动量守恒(自然的，因为纬向平均结构，例如纬向急流包含大气层的大部分角动量)和气流稳定性对纬向急流的基本限制；(2)波动动力学(及相关的涡动量通量)和临界水平的作用；(3)在光伏跳跃上传播的边缘波与在光滑的背景光伏梯度上传播的波的作用；(3)光伏混合作为形成纬向急流的途径，与能量级联的方向无关；(4)示踪剂的混合和传输以及急流作为传输障碍的作用；(5)喷流演变和喷流合并机制；(6)二次环流和通过垂直运动形成陡峭的示踪剂梯度；示踪剂和PV梯度的对准。所涉及的动力过程控制着在地球大气和海洋中观察到的带状结构，以及在气体巨星的大气中观察到的。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可变性、副热带急流和北极振荡、水循环、平流层臭氧恢复、平流层和对流层的动力耦合以及热带外对流层顶的输送和混合。

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.