The MetService team produces both coastal and recreational marine forecasts. Part of these forecasts includes the state of the sea and the swell. But what is the difference?
Firstly, it is important to understand how a wave is described. Figure one shows the different characteristics of a wave.
Figure 1: Wave characteristics
a - wave amplitude. The vertical distance from mean level to crest, measured in metres.
H - wave height. The vertical height from crest to trough, measured in metres. It is equal to twice the amplitude.
L - wave length. The horizontal distance from crest to crest, measured in metres.
T - wave period. For a moving wave, the duration of one cycle from one crest to the