The most common non-directional wave parameters describing wave height and period are single values derived from the wave record. For further background, refer to Wave types and characteristics. Wave parameters are derived either from time series analysis or from spectral analysis, a full overview of the parameters and how they are obtained can be found in Processed wave parameters.
One of the most widely used parameters to characterize a sea state is the significant wave height. Traditionally, the significant wave height is calculated from time series analysis and defined as the mean of the highest one-third of the waves in a record. In spectral analysis, this parameter is instead estimated from the wave spectrum. A commonly used approximation is given in Equation 1,
| \(H_{m0} = 4.0\sqrt{m0}\) | (1) |
where \(m0\) represents the first momentum of the power spectrum. The \(k^{th}\) momentum is defined in Equation 2.
| \(m_{k}=\int f^{k}C\left( f \right)df\) | (2) |
where \(C\) is the power spectrum and \(f\) is the frequency.
The time series-based estimate of the significant wave height is available as the H3 parameter. This parameter requires a direct measurement of the surface elevation (e.g. AST). Comparisons between the two estimates show that Hm0 typically overestimates the significant wave height by approximately 5%.
Other wave height parameters of interest include the maximum wave height (Hmax), defined as the largest wave in the record, and H10, defined as the mean of the highest 10% of waves. These parameters are commonly used in coastal design and assessment and, like H3, require direct measurements of surface elevation (e.g. AST). When only indirect measurements are available, these parameters cannot be derived directly, but can be approximated using linear relationships given in Equation 3 and 4.
| \( H10\ = 1.27 \times Hm0\) | (3) |
\( Hmax\ = 1.67 \times Hm0\) |
(4) |
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