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Namespace Prefixes

Prefix	IRI
dcterms	http://purl.org/dc/terms/
n6	http://vocab.nerc.ac.uk/standard_name/sea_surface_wave_principal_from_direction/
n2	http://vocab.nerc.ac.uk/collection/P07/current/TNCL40SJ/
dc	http://purl.org/dc/elements/1.1/
n9	http://vocab.nerc.ac.uk/collection/P06/current/UAAA/
skos	http://www.w3.org/2004/02/skos/core#
void	http://rdfs.org/ns/void#
rdf	http://www.w3.org/1999/02/22-rdf-syntax-ns#
n12	http://vocab.nerc.ac.uk/.well-known/
owl	http://www.w3.org/2002/07/owl#
xsdh	http://www.w3.org/2001/XMLSchema#
n7	http://purl.org/pav/
n13	http://mmisw.org/ont/cf/parameter/
n10	http://vocab.nerc.ac.uk/collection/P07/current/TNCL40SJ/1/

Statements

Subject Item

n2:

rdf:type

skos:Concept

owl:versionInfo

1

owl:sameAs

n6: n13:sea_surface_wave_principal_from_direction

skos:prefLabel

sea_surface_wave_principal_from_direction

dcterms:identifier

SDN:P07::TNCL40SJ

dc:identifier

SDN:P07::TNCL40SJ

dcterms:date

2024-05-20 20:39:48.0

skos:definition

The wave direction in each frequency band, calculated from the second-order components of the wave directional spectrum. Since there is an ambiguity of 180 degrees in the calculation of Alpha2 (i.e. 90 degrees and 270 degrees result in equivalent spectra), the value closer to Alpha1 is selected. 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}). ALPHA2 is the principal wave direction, which is determined from the second-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.

skos:notation

SDN:P07::TNCL40SJ

skos:altLabel

owl:deprecated

false

skos:note

accepted

void:inDataset

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skos:related

n9:

n7:authoredOn

2024-05-20 20:39:48.0

n7:hasCurrentVersion

n10:

n7:version

1