Editing Sea state (section)

== Sea states in marine engineering ==
In engineering applications, sea states are often characterized by the following two parameters:

* The ''[[significant wave height]]'' ''H''<sub>1/3</sub>  — the mean [[wave height]] of the highest third of the waves.<ref>{{cite book |last=Munk |first=W.H. |title=Proposed uniform procedure for observing waves and interpreting instrument records |publisher=Wave Project at the [[Scripps Institution of Oceanography]] |year=1944 |location=La Jolla, California}}</ref>
* The mean ''[[wave period]]'', ''T''<sub>1</sub>.

In addition to the short-term wave statistics presented above, long-term sea state statistics are often given as a joint frequency table of the significant wave height and the mean wave period. From the long and short-term statistical distributions, it is possible to find the extreme values expected over a given number of years by fitting a extreme value distribution.<ref>{{Cite journal |last=Aarnes |first=Ole Johan |last2=Breivik |first2=Øyvind |last3=Reistad |first3=Magnar |date=2012 |title=Wave Extremes in the Northeast Atlantic |url=https://journals.ametsoc.org/doi/10.1175/JCLI-D-11-00132.1 |journal=Journal of Climate |language=en |volume=25 |issue=5 |pages=1529–1543 |doi=10.1175/JCLI-D-11-00132.1 |issn=0894-8755|hdl=1956/9253 |hdl-access=free }}</ref> The extreme value distribution can then inform an engineer about the most extreme significant wave height to be expected during a lifetime of a ship or offshore structure. Using the [[Response amplitude operator|response amplitude operators]] of the ship, the engineer can then use the extremes in significant wave height and wave period to calculate the most extreme loads that the ship should be able to withstand. Withstanding significant wave heights that happen on average once in 100 years or once in 1000 years is a common demand for design of ships and offshore structures.<ref>{{Cite journal |last=Jonathan |first=Philip |last2=Ewans |first2=Kevin |date=2013 |title=Statistical modelling of extreme ocean environments for marine design: A review |url=https://linkinghub.elsevier.com/retrieve/pii/S002980181300019X |journal=Ocean Engineering |language=en |volume=62 |pages=91–109 |doi=10.1016/j.oceaneng.2013.01.004}}</ref>