Concept
sea_surface_wave_mean_from_direction
| URI | http://vocab.nerc.ac.uk/collection/P07/current/TISEXP3S/ | ||
|---|---|---|---|
| Within Vocab | Climate and Forecast Standard Names | ||
| Alternative Labels | |||
| Definition | The wave direction in each frequency band, calculated from the first-order components of the wave directional spectrum. The full directional wave spectrum is described as a Fourier series: S = a0/2 + a1cos(theta) + b1sin(theta) + a2cos(2theta) + b2sin(2theta). The Fourier coefficients a1, b1, a2, & b2 can be converted to polar coordinates as follows: R1 = (SQRT(a1a1+b1b1))/a0, R2 = (SQRT(a2a2+b2b2))/a0, ALPHA1 = 270.0-ARCTAN(b1,a1), ALPHA2 = 270.0-(0.5*ARCTAN(b2,a2)+{0 or 180, whichever minimizes the difference between ALPHA1 and ALPHA2}). ALPHA1 is the mean wave direction, which is determined from the first-order Fourier coefficients. This spectral parameter is a separate quantity from the bulk parameter (MWDIR), which has the standard name sea_surface_wave_from_direction_at_variance_spectral_density_maximum. The phrase "from_direction" is used in the construction X_from_direction and indicates the direction from which the velocity vector of X is coming. The direction is a bearing in the usual geographical sense, measured positive clockwise from due north. | ||
| Date | 2024-05-20T20:39:48 | ||
| Identifier | SDN:P07::TISEXP3S | ||
| Note | accepted | ||
| Has Current Version | 1 | ||
| version | 1 | ||
| Same As | CF | http://vocab.nerc.ac.uk/standard_name/sea_surface_wave_mean_from_direction/ | Mapping: 439111 |
| MMI | http://mmisw.org/ont/cf/parameter/sea_surface_wave_mean_from_direction | Mapping: 441015 | |
| Related | P06:UAAA |
Degrees | Mapping: 1853534 |
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