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GUIDE WAVE ANALYSIS AND FORECASTING - WMO

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120<br />

Abbreviation/ Definition<br />

Symbol<br />

ANNEX I<br />

hb Breaking depth; water depth at which a wave of given height breaks — m<br />

hPa hectoPascal — unit of pressure<br />

H High pressure centre<br />

H<br />

–<br />

H<br />

Wave height — m (ft)<br />

Average wave height in a record — m (ft)<br />

Hb Breaker wave height — m (ft)<br />

Hc Characteristic wave height (average height of the larger well-formed waves, observed<br />

visually) — m (ft)<br />

Hcombined Wave height for total wave field — m (ft)<br />

Hmax, Hm, Hmax,3h Hm0 Maximum wave height for specified period of time — m (ft)<br />

Wave height derived from energy spectrum, approximately equal to – H1/3; Hm0 = 4 m 1/2<br />

0 —<br />

m (ft)<br />

Hrms Root-mean-square wave height = (8 E/ρwg) 1/2 Hs — m (ft)<br />

Significant wave height = Hm0 or – H1/3, according to specification — m (ft)<br />

HsN, Hs50 N-year, 50-year return value of Hs — m (ft)<br />

Hsea Wind wave height — m (ft)<br />

Hswell Swell height — m (ft)<br />

Hz Zero-crossing wave height (the vertical distance between the highest and lowest value of the<br />

–<br />

H1/n –<br />

H1/3 wave record between two zero-downcrossings or upcrossings)<br />

The average height of the 1/n highest waves — m (ft)<br />

Significant wave height: average of the 1/3 highest waves in a record (approximates to the<br />

characteristic wave height) — m (ft)<br />

Hz Hertz, measure of frequency = 1 cycle per second — s –1<br />

HF High Frequency<br />

HMSO Her Majesty's Stationary Office (UK)<br />

I, (ui, vi) Isallobaric wind vector<br />

IAHR International Association for Hydraulic Research (Delft, Netherlands)<br />

J Wave power — kW/m (of wavefront)<br />

JMA Japan Meteorological Agency<br />

JONSWAP Joint North Sea Wave Proj ect<br />

k; k Wavenumber (2π/λ); vector wavenumber — m –1<br />

km Unit of length, kilometre<br />

kn Unit of speed, knot (1.94 kn = 1 m/s)<br />

kW Unit of power, kilowatt<br />

K Mixing coefficient<br />

Kr Refraction factor<br />

Ks Shoaling factor<br />

KNMI Royal Netherlands Meteorological Institute<br />

L Low pressure centre<br />

L Monin-Obukhov mixing length — m<br />

m Unit of length, metre<br />

mks Metric system of units based on the metre, kilogram and second as the units of length, mass<br />

and time; it forms the basis of the International System of Units (SI)<br />

mn The n-th order moment of the wave spectrum<br />

m0 Moment of zero order; represents the integral of a wave spectrum<br />

m/s Unit of speed, metre per second<br />

ME Mean error

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