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Synchronization and predictability in experimental fluids and climate dynamics

实验流体和气候动力学的同步性和可预测性

基本信息

批准号：
NE/F002157/1
负责人：
Peter Read
金额：
$ 34.16万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF002157%2F1
关键词：
Synchronization predictability experimental fluids climate

项目摘要

A thorough understanding of the environment and climate of the Earth, and the development of methods to predict its future behaviour and responses to changes in factors such as atmospheric composition and external forcing, requires a holistic consideration of the entire Earth system. Such an approach views the Earth in terms of a complicated collection of distinct sub-systems (the troposphere, stratosphere, oceans, cryosphere, land surface and biosphere, for example), all mutually interacting via complex feedback processes and subject to time-varying external forces (such as the diurnal and annual cycles, and other external processes on longer timescales), and leading to complex behaviour that is very difficult to predict. Such a view of the Earth System underpins modern approaches to modelling the Earth's present and past climates, and more recently also to evaluating socio-economic and ecological responses to such changes, such as in NERC's QUEST programme. In a system as complex as the Earth, interactions between sub-systems are likely themselves to be highly complex, intermittent and nonlinear, presenting enormous challenges to the modelling community to represent accurately and realistically. In this context, a knowledge and understanding of the kinds of interactions possible between dynamical systems in the presence of nonlinearity is vital to guide the future development of modelling strategies. In recent years, the study of synchronization phenomena in nonlinear systems has made a number of significant advances in various areas of physics, engineering and the life sciences. The first documented example of synchronization was reported as long ago as 1665 by Christiaan Huygens, who noted the tendency of a pair of pendulum clocks, mounted on a common support, eventually to swing together in synchronized motion, even if they would tend to swing at slightly different speeds if isolated from each other. More recently, the study of such nonlinear frequency entrainment and synchronization has been extended to a much more quantitative understanding of the nature of synchronization, the identification of various forms of imperfect synchronization phenomena (e.g. where synchronization happens for a short while and then breaks up, only to resynchronize a little later), and the generalisation to the study of synchronization effects manifest in coupled chaotic systems. In this project, we will study the range of complex forms of synchronization in a fluid dynamical analogue of the Earth's mid-latitude atmospheric circulation in the laboratory. A fluid placed in a cylindrical tank, and subject to differential heating between the inner and outer radius whilst being rotated about the axis of the cylinder, will spontaneously generate complicated jet streams and wave-like instabilities that are dynamically similar to the jet stream and cyclones that organize mid-latitude weather on the Earth. We have recently developed an apparatus that allows us to couple two of these experiments together in such a way that we can study their interaction and possible synchronization behaviour. This is analogous in some respects to certain kinds of feedback process in the climate system. We plan to carry out an extensive study of the range of possible behaviour of this system, measuring the form and strength of synchronization effects and developing new methods for analysing these effects from timeseries of measurements. These methods will then be applied to real climate data in an attempt to detect and quantify similar synchronization phenomena in the atmosphere and oceans during the past 50-100 years. For the latter part of the study we will concentrate on known cyclic phenomena on timescales ranging from 20-60 days to interannual periods (around 1-3 years).

全面了解地球的环境和气候，发展预测其未来行为和对诸如大气成分和外部强迫等因素变化的反应的方法，需要对整个地球系统进行整体考虑。这种方法将地球看作是不同子系统（例如对流层、平流层、海洋、冰冻圈、陆地表面和生物圈）的复杂集合，所有这些子系统都通过复杂的反馈过程相互作用，并受到时变外力（如日周期和年周期，以及更长时间尺度上的其他外部过程）的影响，并导致非常难以预测的复杂行为。这种对地球系统的看法支持了对地球现在和过去气候进行建模的现代方法，最近也支持了对这些变化的社会经济和生态反应的评估，例如在NERC的QUEST项目中。在像地球这样复杂的系统中，子系统之间的相互作用本身可能是高度复杂的、间歇性的和非线性的，这给建模界提出了准确和真实地表示的巨大挑战。在这种情况下，了解和理解非线性存在下动力系统之间可能存在的各种相互作用，对于指导建模策略的未来发展至关重要。近年来，非线性系统同步现象的研究在物理、工程和生命科学的各个领域取得了许多重大进展。早在1665年，克里斯蒂安·惠更斯（Christiaan Huygens）就报道了第一个记录同步的例子，他注意到一对摆钟，安装在一个共同的支架上，最终会以同步的运动一起摆动，即使它们彼此分开时倾向于以略有不同的速度摆动。最近，对这种非线性频率携带和同步的研究已经扩展到对同步本质的更定量的理解，对各种形式的不完全同步现象的识别（例如，同步发生了很短的时间，然后中断，只是稍后重新同步），并推广到耦合混沌系统中同步效应的研究。在这个项目中，我们将在实验室中研究地球中纬度大气环流流体动力学模拟中复杂形式同步的范围。将液体置于圆柱形罐中，并在围绕圆柱体轴线旋转的同时，受到内外半径之间的不同加热，将自发地产生复杂的喷射流和波状不稳定性，其动态类似于地球上组织中纬度天气的喷射流和气旋。我们最近开发了一种装置，可以让我们把两个实验结合在一起，这样我们就可以研究它们的相互作用和可能的同步行为。这在某些方面类似于气候系统中的某些反馈过程。我们计划对该系统的可能行为范围进行广泛的研究，测量同步效应的形式和强度，并开发从测量时间序列分析这些效应的新方法。然后将这些方法应用于实际气候数据，试图探测和量化过去50-100年间大气和海洋中类似的同步现象。在研究的后半部分，我们将集中研究从20-60天到年际周期（约1-3年）的已知周期现象。