windsea

Windsea is a term used in physical oceanography and maritime meteorology to describe the portion of the ocean surface wave field generated locally by wind action. It is distinguished from swell, the longer-period waves that have traveled beyond their generation area and may include energy from distant winds.

Generation and characteristics: Windsea waves arise when winds blow over water for a sufficient duration and fetch. They tend to have shorter periods and wavelengths than swell, with most energy distributed in higher frequencies. The waves propagate roughly in the wind direction, though the wave field exhibits angular spreading set by the local wind and sea conditions. The relative share of windsea in the observed sea state grows with wind speed, wind duration, and fetch, and declines after wind ceases as existing wind-driven waves dissipate and distant swell becomes more prominent.

Measurement and usage: In spectral wave analyses, the sea state is partitioned into windsea and swell components. Forecasts and buoy data report parameters such as significant wave height, peak period, and the windsea fraction. Coastal and offshore operations use windsea conditions to assess seakeeping, surfability, and harbor safety. Numerical models like SWAN and WAVEWATCH III simulate the windsea component by parameterizing local wind input and dissipation.

Terminology: Some authors use windsea and wind sea interchangeably; others reserve windsea for the locally generated portion of the spectrum. In practical contexts, the term is most relevant where local winds control the sea state, such as in coastal waters and storm-impacted regions.