Movatterモバイル変換

[0]ホーム

Jump to content

Wave height

Edit links

From Wikipedia, the free encyclopedia

Difference between the elevations of a crest and a neighbouring trough

Influid dynamics, thewave height of asurface wave is the difference between theelevations of acrest and a neighboringtrough.^[1]Wave height is a term used bymariners, as well as incoastal,ocean andnaval engineering.

At sea, the termsignificant wave height is used as a means to introduce a well-defined and standardizedstatistic to denote the characteristic height of therandom waves in asea state, includingwind sea andswell. It is defined in such a way that it more or less corresponds to what amariner observes when estimating visually the average wave height.

Definitions

[edit]

Depending on context, wave height may be defined in different ways:

For asine wave, the wave heightH is twice theamplitude (i.e., thepeak-to-peak amplitude):^[1] $H=2a.$
For aperiodic wave, it is simply the difference between themaximum andminimum of the surface elevationz =η(x –c_pt):^[1] $H=\max \left\{\eta (x\,-\,c_{p}\,t)\right\}-\min \left\{\eta (x-c_{p}\,t)\right\},$ withc_p thephase speed (or propagation speed) of the wave. The sine wave is a specific case of a periodic wave.
In random waves at sea, when the surface elevations are measured with awave buoy, the individual wave heightH_m of each individual wave—with aninteger labelm, running from 1 toN, to denote its position in a sequence ofN waves—is the difference in elevation between a wave crest and trough in that wave. For this to be possible, it is necessary to first split the measuredtime series of the surface elevation into individual waves. Commonly, an individual wave is denoted as thetime interval between two successive downward-crossings through theaverage surface elevation (upward crossings might also be used). Then the individual wave height of each wave is again the difference between maximum and minimum elevation in the time interval of the wave under consideration.^[2]

Significant wave height

[edit]

This section is an excerpt fromSignificant wave height.[edit]

Inphysical oceanography, thesignificant wave height (SWH, HTSGW^[3] orH_s) is defined traditionally as the meanwave height (trough tocrest) of the highest third of thewaves (H_1/3). It is usually defined as four times thestandard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment (area) of thewave spectrum.^[4] The symbolH_m0 is usually used for that latter definition. The significant wave height (H_s) may thus refer toH_m0 orH_1/3; the difference in magnitude between the two definitions is only a few percent.SWH is used to characterizesea state, includingwinds andswell.

RMS wave height

[edit]

Another wave-height statistic in common usage is theroot-mean-square (or RMS) wave heightH_rms, defined as:^[2] $H_{\text{rms}}={\sqrt {{\frac {1}{N}}\sum _{m=1}^{N}H_{m}^{2}}},$ withH_m again denoting the individual wave heights in a certaintime series.

Notes

[edit]

^^a ^b ^cKinsman (1984, p. 38)
^^a ^bHolthuijsen (2007, pp. 24–28)
^"About earth :: A global map of wind, weather, and ocean conditions".
^Holthuijsen, Leo H. (2007).Waves in Oceanic And Coastal Waters. Cambridge University Press. p. 70.ISBN 978-0-521-86028-4.

References

[edit]

Holthuijsen, Leo H. (2007),Waves in Oceanic and Coastal Waters, Cambridge University Press,ISBN 978-0-521-86028-4, 387 pages.
Kinsman, Blair (1984),Wind waves: their generation and propagation on the ocean surface, Dover Publications,ISBN 0-486-49511-6, 704 pages.
Phillips, Owen M. (1977),The dynamics of the upper ocean (2nd ed.), Cambridge University Press,ISBN 0-521-29801-6, viii & 336 pages.

v t e Physical oceanography
Waves	Airy wave theory Ballantine scale Benjamin–Feir instability Boussinesq approximation Breaking wave Clapotis Cnoidal wave Cross sea Dispersion Edge wave Equatorial waves Gravity wave Green's law Infragravity wave Internal wave Iribarren number Kelvin wave Kinematic wave Longshore drift Luke's variational principle Miche criterion Mild-slope equation Radiation stress Rogue wave Draupner wave Rossby wave Rossby-gravity waves Sea state Seiche Significant wave height Soliton Stokes drift Stokes problem Stokes wave Swell Trochoidal wave Tsunami megatsunami Undertow Ursell number Wave action Wave base Wave height Wave nonlinearity Wave power Wave radar Wave setup Wave shoaling Wave turbulence Wave–current interaction Waves and shallow water one-dimensional Saint-Venant equations shallow water equations Wind fetch Wind setup Wind wave model
Circulation	Atmospheric circulation Baroclinity Boundary current Coriolis force Coriolis–Stokes force Craik–Leibovich vortex force Downwelling Eddy Ekman layer Ekman spiral Ekman transport El Niño–Southern Oscillation General circulation model Geochemical Ocean Sections Study Geostrophic current Global Ocean Data Analysis Project Gulf Stream Humboldt Current Hydrothermal circulation Langmuir circulation Longshore drift Loop Current Modular Ocean Model Ocean current Ocean dynamical thermostat Ocean dynamics Ocean gyre Overflow Princeton Ocean Model Rip current Subsurface ocean current Sverdrup balance Thermohaline circulation shutdown Upwelling Whirlpool Wind generated current World Ocean Circulation Experiment
Tides	Amphidromic point Earth tide Head of tide Internal tide Lunitidal interval Perigean spring tide Rip tide Rule of twelfths Slack tide Theory of tides Tidal bore Tidal force Tidal power Tidal race Tidal range Tidal resonance Tide gauge Tideline
Landforms	Abyssal fan Abyssal plain Atoll Bathymetric chart Carbonate platform Coastal geography Cold seep Continental margin Continental rise Continental shelf Contourite Guyot Hydrography Knoll Ocean bank Oceanic basin Oceanic plateau Oceanic trench Passive margin Seabed Seamount Submarine canyon Submarine volcano
Plate tectonics	Convergent boundary Divergent boundary Fracture zone Hydrothermal vent Marine geology Mid-ocean ridge Mohorovičić discontinuity Oceanic crust Outer trench swell Ridge push Seafloor spreading Slab pull Slab suction Slab window Subduction Transform fault Vine–Matthews–Morley hypothesis Volcanic arc
Ocean zones	Benthic Deep ocean water Deep sea Littoral Mesopelagic Oceanic Pelagic Photic Surf Swash
Sea level	Deep-ocean Assessment and Reporting of Tsunamis Global Sea Level Observing System North West Shelf Operational Oceanographic System Sea-level curve Sea level drop Sea level rise World Geodetic System
Acoustics	Deep scattering layer Ocean acoustic tomography Sofar bomb SOFAR channel Underwater acoustics
Satellites	Jason-1 OSTM/Jason-2 Jason-3
Related	Acidification Argo Benthic lander Color of water DSVAlvin Marginal sea Marine energy Marine pollution Mooring National Oceanographic Data Center Ocean Explorations Observations Reanalysis Ocean surface topography Ocean temperature Ocean thermal energy conversion Oceanography Outline of oceanography Pelagic sediment Sea surface microlayer Sea surface temperature Seawater Science On a Sphere Stratification Thermocline Underwater glider Water column World Ocean Atlas
Category Commons Oceans portal