Since the sea surface consists of many different types of waves and is generally irregular in both time and space, the sea state is described using statistical parameters such as wave height, period, and direction. To approximate the wave field, a couple of assumptions are usually made:
- Wave decomposition: The wave field can be represented as the sum of many sine waves with different frequencies, amplitudes, and directions. This allows the use of Fourier analysis, a mathematical method that breaks down a complex, periodic function into simpler components (sine and cosine functions). In this way, a time series of wave measurements can be expressed as a limited set of sine waves, providing a more manageable description.
- Statistical stability: The wave field is assumed to be statistically stable, meaning that repeated measurements taken moments apart would yield the same statistical properties. This is referred to as a short-term description of the sea state.
Updated