The Pierson-Moskowitz spectrum (Pierson and
Moskowitz, 1964) is often used as a model spectrum for
a fully developed sea, an idealized equilibrium state
reached when duration and fetch are unlimited. This
spectrum is based on a subset of 420 selected wave
measurements recorded with the shipborne wave
recorder — developed by Tucker (1956) — on board
British ocean weather ships during the five-year period
1955–1960. In its original form, this model spectrum is: