The instruments collect raw wave data that must be processed before it can be used to describe the surface wave field. The resulting wave parameters can be divided into two categories: non-directional parameters (describing wave height and period) and directional parameters (describing wave direction). Wave directions are reported as the direction from which the waves are coming.
Table 1 provides an overview of all available wave parameters, both non-directional and directional. As described in Measurement principles wave parameters are derived either from time series analysis or from spectral analysis. The table indicates how each parameter is obtained.
| Acronym | Description | Note |
| Hm0 |
Significant wave height. Calculated from energy spectrum. \( Hm0\ = 4 \times \sqrt{m0}\) |
|
| H3 |
Mean of the 1/3 largest waves in a record. Time series based estimate (using the zero-crossing method). |
AST only |
| H10 |
Mean of the 1/10 largest waves in a record. Time series based estimate (using the zero-crossing method). When AST is not available, H10 can be estimated by \( H10\ = 1.27 \times Hm0\) |
AST only |
| Hmax |
Largest wave in the record. Time series based estimate (using the zero-crossing method). When AST is not available, H10 can be estimated by \( Hmax\ = 1.67 \times Hm0\) |
AST only |
| Hmean |
Mean values of all waves in the record. Time series based estimate (using the zero-crossing method). |
AST only |
| Tm02 |
Mean period. Calculated from energy spectrum. \( Tm02\ = \sqrt{\frac{m0}{m2}}\) |
|
| Tp |
Peak period. The period of the waves corresponding to the peak frequency. Calculated from the energy spectrum \(Tp\ = \frac{1}{f_{peak}}\) |
|
| Tz |
Mean period. Time series based estimate (using the zero-crossing method). |
AST only |
| T3 |
Period associated with the 1/3 largest waves in the record, H3. Time series based estimate (using the zero-crossing method). |
AST only |
| T10 |
Period associated with the 1/10 largest waves in the record, H10. Time series based estimate (using the zero-crossing method). |
AST only |
| Tmax |
Period associated with the largest wave in the record, Hmax. Time series based estimate (using the zero-crossing method). |
AST only |
| TpDir |
Peak direction. The direction of the waves corresponding to the peak frequency. Calculated from the energy spectrum. |
|
| Spr1 |
Directional spreading. Measure of the directional variance for the waves corresponding to the peak frequency. Calculated from the energy spectrum. \(Spr1=\sqrt{2\times\left( 1-r_{1} \right)}\times \frac{180}{\pi}\) \(r_{1}=\sqrt{A1^2 + B1^2}\) where \(A1^2\) and \(B1^2\) are the first pair of Fourier coefficients at the peak frequency |
|
| Mdir |
Main direction. Weighted average of all the directions in the wave spectrum. Calculated from the energy spectrum. \(Mdir=atan2\left( A1_{band}, B1_{band} \right)\) where \(A1_{band}=\frac{\int S\left( f \right)\times A1\left( f \right)}{\int S\left( f \right)}\) \(B1_{band}=\frac{\int S\left( f \right)\times B1\left( f \right)}{\int S\left( f \right)}\) and \(band\) is the entire frequency range of the energy spectrum |
|
| Unidirectivity index |
Measure of how much of the wave energy over the full spectrum is from a single direction. Value of 1.0 indicates the energy is from one primary direction. Calculated from energy spectrum. |
Updated