Laboratory studies of equatorially trapped waves using ferrofluid

1997 ◽  
Vol 338 ◽  
pp. 35-58 ◽  
Author(s):  
DANIEL R. OHLSEN ◽  
PETER B. RHINES
Keyword(s):  
Fluid Dynamics ◽  
Rotation Rate ◽  
Large Scale ◽  
Rossby Waves ◽  
Low Frequency ◽  
Laboratory Studies ◽  
Geophysical Fluid Dynamics ◽  
Vertical Projection ◽  
Planetary Rotation ◽  
Oceanic Flows

We introduce a new technique to model spherical geophysical fluid dynamics in the terrestrial laboratory. The local vertical projection of planetary vorticity, f, varies with latitude on a rotating spherical planet and allows an important class of waves in large-scale atmospheric and oceanic flows. These Rossby waves have been extensively studied in the laboratory for middle and polar latitudes. At the equator f changes sign where gravity is perpendicular to the planetary rotation. This geometry has made laboratory studies of geophysical fluid dynamics near the equator very limited. We use ferrofluid and static magnetic fields to generate nearly spherical geopotentials in a rotating laboratory experiment. This system is the laboratory analogue of those large-scale atmospheric and oceanic flows whose horizontal motions are governed by the Laplace tidal equations. As the rotation rate in such a system increases, waves are trapped to latitudes near the equator and the dynamics can be formulated on the equatorial β-plane. This transition from planetary modes to equatorially trapped modes as the rotation rate increases is observed in the experiments. The equatorial β-plane solutions of non-dispersive Kelvin waves propagating eastward and non-dispersive Rossby waves propagating westward at low frequency are observed in the limit of rotation fast compared to gravity wave speed.

scholarly journals Applications of large deviation theory in geophysical fluid dynamics and climate science

2021 ◽  
Author(s):  
Vera Melinda Gálfi ◽  
Valerio Lucarini ◽  
Francesco Ragone ◽  
Jeroen Wouters
Keyword(s):  
Fluid Dynamics ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Large Deviation ◽  
Rare Event ◽  
Low Frequency ◽  
Climate Science ◽  
Geophysical Fluid Dynamics ◽  
Large Deviation Theory ◽  
Deviation Theory

AbstractThe climate is a complex, chaotic system with many degrees of freedom. Attaining a deeper level of understanding of climate dynamics is an urgent scientific challenge, given the evolving climate crisis. In statistical physics, many-particle systems are studied using Large Deviation Theory (LDT). A great potential exists for applying LDT to problems in geophysical fluid dynamics and climate science. In particular, LDT allows for understanding the properties of persistent deviations of climatic fields from long-term averages and for associating them to low-frequency, large-scale patterns. Additionally, LDT can be used in conjunction with rare event algorithms to explore rarely visited regions of the phase space. These applications are of key importance to improve our understanding of high-impact weather and climate events. Furthermore, LDT provides tools for evaluating the probability of noise-induced transitions between metastable climate states. This is, in turn, essential for understanding the global stability properties of the system. The goal of this review is manifold. First, we provide an introduction to LDT. We then present the existing literature. Finally, we propose possible lines of future investigations. We hope that this paper will prepare the ground for studies applying LDT to solve problems encountered in climate science and geophysical fluid dynamics.

Fundamentals of the Theory of Rotating Fluids

1963 ◽  
Vol 30 (4) ◽  
pp. 481-485 ◽  
Author(s):  
L. N. Howard
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
Mathematical Models ◽  
Rotating Flows ◽  
Laboratory Studies ◽  
Geophysical Fluid Dynamics ◽  
Rotating Fluids ◽  
Ekman Boundary Layer ◽  
Physical Phenomena

This paper gives an expository survey of some of the principal mathematical models which have been used in the theory of rotating fluids, together with a discussion of several explicit examples. Some of these examples are related to geophysical fluid dynamics; others more directly to laboratory studies. In all cases the examples have been selected to illustrate some of the most important physical phenomena which are characteristic of rotating flows and distinguish them from other fluid motions. Physical concepts, such as the Taylor-Proudman effects, the Ekman boundary layer, and Rayleigh’s analogy, which have proved useful in obtaining a general understanding of rotating fluids, are presented and discussed.

Dynamic Radiative–Convective Equilibria Using GCM Column Physics

2007 ◽  
Vol 64 (1) ◽  
pp. 228-238 ◽  
Author(s):  
Isaac M. Held ◽  
Ming Zhao ◽  
Bruce Wyman
Keyword(s):  
Fluid Dynamics ◽  
Large Scale ◽  
Homogeneous Model ◽  
Horizontal Resolution ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Geophysical Fluid Dynamics ◽  
Convection Scheme ◽  
Cloud Feedbacks ◽  
The Tropics ◽  
Convective Organization

Abstract The behavior of a GCM column physics package in a nonrotating, doubly periodic, homogeneous setting with prescribed SSTs is examined. This radiative–convective framework is proposed as a useful tool for studying some of the interactions between convection and larger-scale dynamics and the effects of differing modeling assumptions on convective organization and cloud feedbacks. For the column physics utilized here, from the Geophysical Fluid Dynamics Laboratory (GFDL) AM2 model, many of the properties of the homogeneous, nonrotating model are closely tied to the fraction of precipitation that is large-scale, rather than convective. Significant large-scale precipitation appears above a critical temperature and then increases with further increases in temperature. The amount of large-scale precipitation is a function of horizontal resolution and can also be controlled by modifying the convection scheme, as is illustrated here by modifying assumptions concerning entrainment into convective plumes. Significant similarities are found between the behavior of the homogeneous model and that of the Tropics of the parent GCM when ocean temperatures are increased and when the convection scheme is modified.

scholarly journals Shape and size of large-scale vortices: A generic fluid pattern in geophysical fluid dynamics

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Louis-Alexandre Couston ◽  
Daniel Lecoanet ◽  
Benjamin Favier ◽  
Michael Le Bars
Keyword(s):  
Fluid Dynamics ◽  
Large Scale ◽  
Geophysical Fluid Dynamics ◽  
Shape And Size

Geophysical Fluid Dynamics

2018 ◽  
Author(s):  
Vladimir Zeitlin
Keyword(s):  
Fluid Dynamics ◽  
Large Scale ◽  
Water Model ◽  
Time Averaging ◽  
Editorial Office ◽  
Geophysical Fluid Dynamics ◽  
Wave Interactions ◽  
Wave Dynamics ◽  
Rotating Shallow Water ◽  
Nonlinear Wave Interactions

The book explains the key notions and fundamental processes in the dynamics of the fluid envelopes of the Earth (transposable to other planets), and methods of their analysis, from the unifying viewpoint of rotating shallow-water model (RSW). The model, in its one- or two-layer versions, plays a distinguished role in geophysical fluid dynamics, having been used for around a century for conceptual understanding of various phenomena, for elaboration of approaches and methods, to be applied later in more complete models, for development and testing of numerical codes and schemes of data assimilations, and many other purposes. Principles of modelling of large-scale atmospheric and oceanic flows, and corresponding approximations, are explained and it is shown how single- and multi-layer versions of RSW arise from the primitive equations by vertical averaging, and how further time-averaging produces celebrated quasi-geostrophic reductions of the model. Key concepts of geophysical fluid dynamics are exposed and interpreted in RSW terms, and fundamentals of vortex and wave dynamics are explained in Part 1 of the book, which is supplied with exercises and can be used as a textbook. Solutions of the problems are available at Editorial Office by request. In-depth treatment of dynamical processes, with special accent on the primordial process of geostrophic adjustment, on instabilities in geophysical flows, vortex and wave turbulence and on nonlinear wave interactions follows in Part 2. Recently arisen new approaches in, and applications of RSW, including moist-convective processes constitute Part 3.

scholarly journals Effect of Overturning Circulation on Long Equatorial Waves: A Low-Frequency Cutoff

2018 ◽  
Vol 75 (5) ◽  
pp. 1721-1739 ◽  
Author(s):  
Amanda Back ◽  
Joseph A. Biello
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Meridional Circulation ◽  
Low Frequency ◽  
Hadley Cell ◽  
Equatorial Waves ◽  
Kelvin Wave ◽  
Background Flow ◽  
Overturning Circulation ◽  
Equatorial Wave

Zonally long tropical waves in the presence of a large-scale meridional and vertical overturning circulation are studied in an idealized model based on the intraseasonal multiscale moist dynamics (IMMD) theory. The model consists of a system of shallow-water equations describing barotropic and first baroclinic vertical modes coupled to one another by the zonally symmetric, time-independent background circulation. To isolate the effects of the meridional circulation alone, an idealized background flow is chosen to mimic the meridional and vertical components of the flow of the Hadley cell; the background flow meridionally converges and rises at the equator. The resulting linear eigenvalue problem is a generalization of the long-wave-scaled version of Matsuno’s equatorial wave problem with the addition of meridional and vertical advection. The results demonstrate that the meridional circulation couples equatorially trapped baroclinic Rossby waves to planetary, barotropic free Rossby waves. The meridional circulation also causes the Kelvin wave to develop an equatorially trapped barotropic component, imparting a westward-tilted vertical structure to the wave. The total energy of the linear system is positive definite, so all waves are shown to be neutrally stable. A critical layer exists at latitudes where the meridional background flow vanishes, resulting in a minimum frequency cutoff for physically feasible waves. Therefore, linear Matsuno waves with periods longer than the vertical transport time of the meridional circulation do not exist in the equatorial waveguide. This implies a low-frequency cutoff for long equatorial waves.

Lectures on Geophysical Fluid Dynamics

1998 ◽  
Author(s):  
Rick Salmon
Keyword(s):  
Fluid Dynamics ◽  
Ocean Circulation ◽  
Large Scale ◽  
Geophysical Fluid Dynamics ◽  
Geostrophic Turbulence ◽  
Scientific Fields

Lectures on Geophysical Fluid Dynamics offers an introduction to several topics in geophysical fluid dynamics, including the theory of large-scale ocean circulation, geostrophic turbulence, and Hamiltonian fluid dynamics. Since each chapter is a self-contained introduction to its particular topic, the book will be useful to students and researchers in diverse scientific fields.

scholarly journals Low-frequency variability of the Kuroshio Extension

2009 ◽  
Vol 16 (6) ◽  
pp. 665-675 ◽  
Author(s):  
S. Pierini ◽  
H. A. Dijkstra
Keyword(s):  
Nonlinear Dynamics ◽  
Large Scale ◽  
Rossby Waves ◽  
Kuroshio Extension ◽  
Baroclinic Instability ◽  
Low Frequency ◽  
Wave Dynamics ◽  
Low Frequency Variability ◽  
Low Dimensional ◽  
The Kuroshio

Abstract. In this paper, we provide a review of recent results targeted at the understanding of the low-frequency variability of the Kuroshio Extension. We provide the background and main arguments of two views which have recently been proposed to explain this variability. In the first view, wind-induced Rossby waves and the effects of mesocale eddies are crucial. The second view is based on low-dimensional equivalent-barotropic large-scale nonlinear dynamics, with neither Rossby wave dynamics nor baroclinic instability being important. Results from models supporting each view are discussed and confronted with results from available observations.

Oceanic Teleconnections: Remote Response to Decadal Wind Forcing

2003 ◽  
Vol 33 (8) ◽  
pp. 1604-1617 ◽  
Author(s):  
Paola Cessi ◽  
Pantxika Otheguy
Keyword(s):  
Northern Hemisphere ◽  
Mass Flux ◽  
Large Scale ◽  
Rossby Waves ◽  
Low Frequency ◽  
Wind Forcing ◽  
Time Dependent ◽  
Eastern Boundary ◽  
Simple Geometry ◽  
Dependent Mass

Abstract The transhemispheric and interbasin response to time-dependent wind forcing localized in the Northern Hemisphere of a single basin is examined using the reduced-gravity shallow-water equations in domains of simple geometry. On decadal timescales, the pressure on the eastern boundary fluctuates synchronously in both hemispheres and thus communicates a signal to latitudes distant from the forcing. The signal then penetrates into the interior through westward radiation of Rossby waves. Associated with the eastern boundary pressure fluctuation is a time-dependent mass flux across the equator that, in a single basin, is balanced by a storage of mass in the unforced hemisphere. Two oceanic basins connected by a reentrant channel at the high-latitude edge of the Southern Hemisphere are then considered. Again the forcing is confined to the Northern Hemisphere of one basin only. In this geometry the time-dependent mass flux across the equator of the forced basin is not entirely balanced within the same basin, but induces a mass flux into the unforced basin, while the mass heaving within the periodic channel is negligible. This process is illustrated by considering winds oscillating at a period on the same order as the Rossby wave transit time in high latitudes. The interhemispheric and interbasin teleconnection is achieved by a combination of long Rossby waves and large-scale, low-frequency gravity waves forced by the Rossby signal. These disturbances share no characteristics of Kelvin waves; that is, they are not boundary trapped.

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