2005-08-10T10:05:06 More information: NDBC Waves Luis Bermudez MMI Variable definition Variable Spectral Wave Density Energy in (meter*meter)/Hz, for each frequency bin. Spectral Wave Density ALPHA2 Principal Wave Directions for each frequency bin derived from Longuet-Higgins Fourier Coefficients. ALPHA2 The vertical distance between any wind wave crest and the succeeding wind wave trough (independent of swell waves). Wind Wave Height Wind Wave Height Swell Direction The compass direction from which the swell waves are coming from. Swell Direction ALPHA1 ALPHA1 Mean Wave Directions for each frequency bin derived from the Longuet-Higgins Fourier Coefficients. Period of all waves during the wave sampling period. Average Wave Period Average Wave Period Dominant Wave Period Dominant Wave Period The period with the maximum wave energy. Swell Height Swell Height The vertical distance between any swell crest and the succeeding swell wave trough. The compass direction (degrees) from which the wind waves are coming. Wind Wave Direction Wind Wave Direction Second normalized polar coordinate for each frequency bin derived from the Longuet-Higgins Coefficients. R2 R2 Mean Wave Direction The direction corresponding to energy of the Dominant Wave Period. The units are degrees from true North just like wind direction. Mean Wave Direction The average of the highest one-third of all of the wave heights during the wave sampling period. Significant Wave Height Significant Wave Height The time (in seconds) that it takes successive wind wave crests or troughs to pass a fixed point. Wind Wave Period Wind Wave Period R1 R1 First normalized polar coordinate for each frequency bin derived from the Longuet-Higgins Coefficients. The ratio of wave height to wave length and is an indicator of wave stability. When wave steepness exceeds a 1/7 ratio; the wave becomes unstable and begins to break. Wave Steepness Wave Steepness Swell Period Swell Period Swell Period is the time (usually measured in seconds) that it takes successive swell wave crests or troughs pass a fixed point. Spectral Wave Direction Mean wave direction, in degrees from true North, for each frequency bin. Spectral Wave Direction