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Sverdrup Wave
A Sverdrup wave (also known as Poincaré wave, or rotational gravity wave Kundu, P. K., and L. M. Cohen. "Fluid mechanics, 638 pp." Academic, Calif (1990).) is a wave in the ocean, or large lakes, which is affected by gravity and Earth's rotation (see Coriolis effect). For a non-rotating fluid, shallow water waves are affected only by gravity (see Gravity wave), where the phase velocity of shallow water gravity wave (''c'') can be noted as : c = (gH)^ and the group velocity (''c''g) of shallow water gravity wave can be noted as : c_\mathrm=(gH)^ i.e. c=c_\mathrm where ''g'' is gravity, ''λ'' is the wavelength and ''H'' is the total depth. Derivation When the fluid is rotating, gravity waves with a long enough wavelength (discussed below) will also be affected by rotational forces. The linearized, shallow-water equations with a constant rotation rate, ''f0'', are Vallis, Geoffrey K. Atmospheric and oceanic fluid dynamics: fundamentals and large-scale circulation. Cambridge Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coriolis Effect
In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise (or counterclockwise) rotation, the force acts to the right. Deflection of an object due to the Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force appeared in an 1835 paper by French scientist Gaspard-Gustave de Coriolis, in connection with the theory of water wheels. Early in the 20th century, the term ''Coriolis force'' began to be used in connection with meteorology. Newton's laws of motion describe the motion of an object in an inertial (non-accelerating) frame of reference. When Newton's laws are transformed to a rotating frame of reference, the Coriolis and centrifugal accelerations appe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Wave
In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a ''wave orbit''. Gravity waves on an air–sea interface of the ocean are called surface gravity waves (a type of surface wave), while gravity waves that are the body of the water (such as between parts of different densities) are called ''internal waves''. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides. The period of wind-generated gravity waves on the free surface of the Earth's ponds, lakes, seas and oceans are predominantly between 0.3 and 30 secon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Velocity
The phase velocity of a wave is the rate at which the wave propagates in any medium. This is the velocity at which the phase of any one frequency component of the wave travels. For such a component, any given phase of the wave (for example, the crest) will appear to travel at the phase velocity. The phase velocity is given in terms of the wavelength (lambda) and time period as :v_\mathrm = \frac. Equivalently, in terms of the wave's angular frequency , which specifies angular change per unit of time, and wavenumber (or angular wave number) , which represent the angular change per unit of space, :v_\mathrm = \frac. To gain some basic intuition for this equation, we consider a propagating (cosine) wave . We want to see how fast a particular phase of the wave travels. For example, we can choose , the phase of the first crest. This implies , and so . Formally, we let the phase and see immediately that and . So, it immediately follows that : \frac = -\frac \frac = \frac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter ''lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) that a wav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion Relation
In the physical sciences and electrical engineering, dispersion relations describe the effect of dispersion on the properties of waves in a medium. A dispersion relation relates the wavelength or wavenumber of a wave to its frequency. Given the dispersion relation, one can calculate the phase velocity and group velocity of waves in the medium, as a function of frequency. In addition to the geometry-dependent and material-dependent dispersion relations, the overarching Kramers–Kronig relations describe the frequency dependence of wave propagation and attenuation. Dispersion may be caused either by geometric boundary conditions (waveguides, shallow water) or by interaction of the waves with the transmitting medium. Elementary particles, considered as matter waves, have a nontrivial dispersion relation even in the absence of geometric constraints and other media. In the presence of dispersion, wave velocity is no longer uniquely defined, giving rise to the distinction of phase ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rossby Radius Of Deformation
In atmospheric dynamics and physical oceanography, the Rossby radius of deformation is the length scale at which rotational effects become as important as buoyancy or gravity wave effects in the evolution of the flow about some disturbance. For a barotropic ocean: L_R \equiv \frac, where \,g is the gravitational acceleration, \,D is the water depth, and \,f is the Coriolis parameter. For ''f'' = 1×10−4 s−1 appropriate to 45° latitude, g = 9.81 m/s^2 and ''D'' = 4 km, ''LR'' ≈ 2000 km; using the same latitude and gravity but changing D to 40 m; ''LR'' ≈ 200 km. The ''n''th baroclinic Rossby radius is: : L_ \equiv \frac, where \,N is the Brunt–Väisälä frequency, \,H is the scale height, and ''n'' = 1, 2, .... In Earth's atmosphere, the ratio ''N''/''f''0 is typically of order 100, so the Rossby radius is about 100 times the vertical scale height, ''H''. For a vertical scale associated with the height of the tropopause, ''L''''R'', 1 & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kelvin Wave
A Kelvin wave is a wave in the ocean or atmosphere that balances the Earth's Coriolis force against a topographic boundary such as a coastline, or a waveguide such as the equator. A feature of a Kelvin wave is that it is non-dispersive, i.e., the phase speed of the wave crests is equal to the group speed of the wave energy for all frequencies. This means that it retains its shape as it moves in the alongshore direction over time. A Kelvin wave (fluid dynamics) is also a long scale perturbation mode of a vortex in superfluid dynamics; in terms of the meteorological or oceanographical derivation, one may assume that the meridional velocity component vanishes (i.e. there is no flow in the north–south direction, thus making the momentum and continuity equations much simpler). This wave is named after the discoverer, Lord Kelvin (1879). Coastal Kelvin wave In a stratified ocean of mean depth ''H'', perturbed by some amount ''η'', free waves propagate along coastal boundaries (and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rossby Wave
Rossby waves, also known as planetary waves, are a type of inertial wave naturally occurring in rotating fluids. They were first identified by Sweden-born American meteorologist Carl-Gustaf Arvid Rossby. They are observed in the atmospheres and oceans of planets owing to the rotation of the planet. Atmospheric Rossby waves on Earth are giant meanders in high-altitude winds that have a major influence on weather. These waves are associated with pressure systems and the jet stream (especially around the polar vortices). Oceanic Rossby waves move along the thermocline: the boundary between the warm upper layer and the cold deeper part of the ocean. Rossby wave types Atmospheric waves Atmospheric Rossby waves result from the conservation of potential vorticity and are influenced by the Coriolis force and pressure gradient. The rotation causes fluids to turn to the right as they move in the northern hemisphere and to the left in the southern hemisphere. For example, a fluid that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geophysical Fluid Dynamics
Geophysical fluid dynamics, in its broadest meaning, refers to the fluid dynamics of naturally occurring flows, such as lava flows, oceans, and planetary atmospheres, on Earth and other planets. Two physical features that are common to many of the phenomena studied in geophysical fluid dynamics are rotation of the fluid due to the planetary rotation and stratification (layering). The applications of geophysical fluid dynamics do not generally include the circulation of the mantle, which is the subject of geodynamics, or fluid phenomena in the magnetosphere. Fundamentals To describe the flow of geophysical fluids, equations are needed for conservation of momentum (or Newton's second law) and conservation of energy. The former leads to the Navier–Stokes equations which cannot be solved analytically (yet). Therefore, further approximations are generally made in order to be able to solve these equations. First, the fluid is assumed to be incompressible. Remarkably, this works we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sverdrup
In oceanography, the sverdrup (symbol: Sv) is a non- SI metric unit of volumetric flow rate, with equal to . It is equivalent to the SI derived unit cubic hectometer per second (symbol: hm3/s or hm3⋅s−1): 1 Sv is equal to 1 hm3/s. It is used almost exclusively in oceanography to measure the volumetric rate of transport of ocean currents. It is named after Harald Sverdrup. One sverdrup is about five times what is carried by the world’s largest river, the Amazon. In the context of ocean currents, a volume of one million cubic meters may be imagined as a "slice" of ocean with dimensions × × (width × length × thickness). At this scale, these units can be more easily compared in terms of width of the current (several km), depth (hundreds of meters), and current speed (as meters per second). Thus, a hypothetical current wide, 500 m (0.5 km) deep, and moving at 2 m/s would be transporting of water. The sverdrup is distinct from the SI sievert unit or th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harald Sverdrup (oceanographer)
Harald Ulrik Sverdrup (15 November 1888 – 21 August 1957) was a Norwegian oceanographer and meteorologist. He was director of Scripps Institution of Oceanography and director of the Norwegian Polar Institute. Background He was born at Sogndal in Sogn og Fjordane, Norway. He was the son of Lutheran theologian Edvard Sverdrup (1861–1923) and Maria Vollan (1865–1891). His sister Mimi Sverdrup Lunden (1894–1955) was an educator and author. His brother Leif Sverdrup (1898–1976) was a General with the U.S. Army Corps of Engineers. His brother Einar Sverdrup (1895–1942) was CEO of Store Norske Spitsbergen Kulkompani. Sverdrup was a student at Bergen Cathedral School in 1901 before graduating in 1906 at Kongsgård School in Stavanger. He graduated cand. real. in 1914 from University of Oslo. He studied under Vilhelm Bjerknes and earned his Dr. Philos. at the University of Leipzig in 1917. Career He was the scientific director of the North Polar expeditio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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