Zonation

分区

• 批准号: 1057838
• 负责人: William Young
• 金额: $ 52.62万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-04-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1057838&HistoricalAwards=false
• 关键词: Zonation

Zonal jets are the result of a poorly understood process via which spontaneously arising Reynolds stresses destroy an initial state of spatially homogeneous beta-plane turbulence. The ultimate equilibration of this instability results in a mature pattern of zonal jets, co-existing with turbulence. All properties of the turbulence, particularly the transport of scalars and potential vorticity, are substantially modified by the jets. This project will develop new approaches to quantitatively analyzing the jet-forming instability and parameterizing transport in these flows. The main hypothesis is that the instability is a transfer of energy, non-local in wave-number, from the forcing scale directly to the jet scale. Preliminary results are supportive of this hypothesis and suggest that negative eddy viscosity may connect the momentum fluxes to mean shear. Essential to the proposal is understanding and modeling the nonlinear feedbacks required to saturate the instability. In physical oceanography there are several proposals for the parameterization of eddy heat and scalar fluxes. Lateral or layerwise momentum fluxes have been almost ignored in this discussion, with the assumption that this processes is unimportant on large scales. Compelling observational evidence that zonal jets exist in the ocean, imply a failure of this approximation. The pressing oceanographic problem addressed by this proposal is the origin of negative viscosity momentum fluxes, and implications for the transport of tracers.The dynamics of zonal flows has important implications for oceanography, meteorology, planetary physics and plasma physics. Structure formation in the midst of a turbulent flow is a striking physical phenomenon, and zonal flows driven by turbulent Reynolds stresses are a foremost example. The mechanism of zonal flow saturation and the question of how, quantitatively, zonal flows figure in the regulation of heat and potential vorticity fluxes are not well understood. The project will provide physically-rooted parameterizations of eddy momentum fluxes, which might be used in coarse resolution climate models. A graduate student at Scripps Institution of Oceanography will receive training in the areas of theoretical problem formulation, geophysical fluid dynamics, applied mathematics, analysis and scientific computation.

纬向射流是一个人们知之甚少的过程的结果，通过该过程自发产生的雷诺应力破坏了空间均匀β平面湍流的初始状态。 这种不稳定性的最终平衡导致了与湍流共存的成熟的纬向急流模式。 湍流的所有特性，特别是标量和位涡的传输，都会被射流显着改变。 该项目将开发新方法来定量分析射流形成的不稳定性并参数化这些流中的传输。 主要假设是不稳定性是波数非局域的能量从强迫尺度直接转移到喷流尺度。 初步结果支持这一假设，并表明负涡流粘度可能将动量通量与平均剪切联系起来。 该提案的关键是理解和建模饱和不稳定性所需的非线性反馈。 在物理海洋学中，有几种关于涡热和标量通量参数化的建议。 在本次讨论中，横向或层向动量通量几乎被忽略，假设该过程在大尺度上并不重要。 令人信服的观测证据表明海洋中存在纬向急流，这意味着这种近似方法是失败的。 该提案解决的紧迫海洋学问题是负粘度动量通量的起源，以及对示踪剂传输的影响。纬向流的动力学对海洋学、气象学、行星物理学和等离子体物理学具有重要意义。 湍流中的结构形成是一种引人注目的物理现象，由湍流雷诺应力驱动的纬向流就是一个最重要的例子。 纬向流饱和的机制以及纬向流如何定量地影响热和位涡通量的调节问题尚不清楚。 该项目将提供涡动量通量的物理参数化，可用于粗分辨率气候模型。 斯克里普斯海洋学研究所的研究生将接受理论问题表述、地球物理流体动力学、应用数学、分析和科学计算等领域的培训。