Ocean wave.

Wave clouds over Theresa, Wisconsin, USA. Wisconsin ( or wɪˈskɑnsɨn (French Ouisconsin) is one of the fifty United States of America, located in the north central part of the United States The United States of America —commonly referred to as the

Atmospheric gravity waves as seen from space.

NASA satellite image of a gravity wave cloud pattern formed in the wake of the Île Amsterdam, a volcanic island in the southern Indian Ocean. A wake is the region of Turbulence immediately to the rear of a solid body caused by the flow of Air or Water around the body New Amsterdam or Île Amsterdam ˈilɑmstəˈdɑm (meaning Amsterdam island after the Dutch Capital) is a French The Indian Ocean is the third largest of the world's Oceanic divisions covering about 20% of the water on the Earth 's surface

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two mediums (e. Fluid dynamics is the sub-discipline of Fluid mechanics dealing with fluid flow: Fluids ( Liquids and Gases in motion FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code An interface is a surface forming a common boundary among two different phases, such as an insoluble Solid and a Liquid, two immiscible liquids or a liquid g. the atmosphere or ocean) which has the restoring force of gravity or buoyancy. In Physics, a force is whatever can cause an object with Mass to Accelerate. Gravitation is a natural Phenomenon by which objects with Mass attract one another In Physics, buoyancy ( BrE IPA: /ˈbɔɪənsi/ is the upward Force on an object produced by the surrounding liquid or gas in which it is

When a fluid parcel is displaced on an interface or internally to a region with a different density, gravity restores the parcel toward equilibrium resulting in an oscillation about the equilibrium state or wave orbit. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and Gravity waves on an air-sea interface are called surface gravity waves or surface waves while internal gravity waves are called internal waves. In Physics, surface wave can refer to a Mechanical wave that propagates along the interface between differing media usually two fluids with different densities Internal waves are Gravity waves that oscillate within rather than on the surface of a fluid medium Ocean waves generated by wind are examples of gravity waves. Ocean surface waves are Surface waves that occur on the Free surface of the Ocean.

Wind waves, as their name suggests, are generated by wind transferring energy from the atmosphere to the ocean's surface. At first capillary waves form on the ocean surface and grow in height at a linear rate proportional to the wind speed (as explained by Miles 1957; 1959). A capillary wave is a Wave travelling along the interface between two fluids whose dynamics are dominated by the effects of Surface tension. Once these small waves have formed they start to interact with the atmosphere through pressure differences and due to the ocean surface roughness. The waves grow at rates exponentially proportional to the wind speed (as explained by Phillips 1957), producing larger and larger waves. This Miles-Phillips Mechanism process can continue until an equilibrium is reached, or until the wind stops transferring energy to the waves (i. e. blowing them along) or when they run out of ocean distance, also known as fetch length.

Gravity waves have a period of between 1 and 30 seconds (1 Hz to 0. 033 Hz). Alternatively, infragravity waves generally have a period between 30 seconds to 5 minutes (0. 05 to 0. 005 Hz). Infragravity waves can be felt rather than seen as they have a much greater wave energy.

Atmosphere dynamics on Earth

Since the fluid is a continuous medium, a traveling disturbance will result. In Mathematics, a continuous function is a function for which intuitively small changes in the input result in small changes in the output In the earth's atmosphere, gravity waves are important for transferring momentum from the troposphere to the mesosphere. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and This article is about the atmospheric mesosphere for the Earth's mantle see Mesosphere (mantle. Gravity waves are generated in the troposphere by frontal systems or by airflow over mountains. A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. A mountain is a Landform that extends above the surrounding Terrain in a limited area with a peak At first waves propagate through the atmosphere without affecting its mean velocity. In Mathematics and Statistics, the arithmetic Mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided In Physics, velocity is defined as the rate of change of Position. But as the waves reach more rarefied air at higher altitudes, their amplitude increases, and nonlinear effects cause the waves to break, transferring their momentum to the mean flow. Altitude is the Elevation of a point or object from a known level or datum (plural data Amplitude is the magnitude of change in the oscillating variable with each Oscillation, within an oscillating system This article describes the use of the term nonlinearity in mathematics

This process plays a key role in controlling the dynamics of the middle atmosphere. In physics the term dynamics customarily refers to the time evolution of physical processes

The clouds in gravity waves can look like Altostratus undulatus clouds, and are sometimes confused with them, but the formation mechanism is different. The altostratus undulatus is a type of low Altocumulus cloud with signature undulations within it

Quantitative description

The phase speed c of a linear gravity wave with wavenumber k is given by the formula

where g is the acceleration due to gravity. Since c = ω / k is the phase speed in terms of the frequency ω and the wavenumber, the gravity wave frequency can be expressed as

The group velocity of a wave (that is, the speed at which a wave packet travels) is given by

and thus for a gravity wave,

The group velocity is one half the phase velocity. A wave in which the group and phase velocities differ is called dispersive.

References

• Dr. Steven Koch, Hugh D. Cobb, III and Neil A. Stuart, "Notes on Gravity Waves - Operational Forecasting and Detection of Gravity Waves Weather and Forecasting". NOAA, Eastern Region Site Server. The National Oceanic and Atmospheric Administration ( NOAA) is a scientific agency within the United States Department of Commerce focused on the conditions of the
• Gill, A. E. , "Gravity wave". Atmosphere Ocean Dynamics, Academic Press, 1982.

See also

• Cloud street
• Lee waves
• Infragravity waves

External links

• Gallery of cloud gravity waves over Iowa
• Time-lapse video of gravity waves over Iowa
• Water Waves Wiki