Long-term Distribution

probability distribution of a variable over a long time scale

NOTE The time scale exceeds the duration of a sea state, in which the statistics are assumed constant (see short-term distribution in 3.29). The time scale is hence comparable to a season or to the design service life of a structure.

EXAMPLE Long-term distributions of

⎯ significant wave height,

⎯ significant wave height in the months May to September,

⎯ individual wave heights,

⎯ current speeds (such as for the vortex induced vibrations of drilling risers),

⎯ scatter diagrams with the joint distribution of significant wave height and wave period (such as for a fatigue analysis), or ⎯ a particular action effect.

Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global Standards

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