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Directional Wave Observations

Directional Wave Observations. 1) Da Basics 2) Remote Sensing v. In Situ : It’s all good. 3) Estimating directional wave properties. 4) Measurement accuracy and user needs. 5) A Recipe for instrument evaluation. The Basics: Estimating the Motion of a Sea Surface Particle. z. z. y. dz/dx,

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Directional Wave Observations

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  1. Directional Wave Observations 1) Da Basics 2) Remote Sensing v. In Situ : It’s all good. 3) Estimating directional wave properties. 4) Measurement accuracy and user needs. 5) A Recipe for instrument evaluation.

  2. The Basics: Estimating the Motion of a Sea Surface Particle z z y dz/dx, dz/dy The Big 3 x w v X, Y, Z u Pressure Sensors Accelerometers Tilt sensors Angular Rate Sensors Acoustic Sensors Radar Lidar

  3. In-Situ and Remotely Sensed Waves O(cm) X,Y,Z Accuracy Time Coverage Spatial Coverage Method In situ SAR,LIDAR HF, X-Band Radar In situ and remote sensing systems are complimentary, NOT redundant.

  4. The Big 3: X, Y, Z  Time Series Analysis  The Fab 5: S(f),a1(f),b1(f),a2(f),b2(f) !! S

  5. - mean direction - directional spread - skewness - kurtosis or, in NDBC format - first-moment mean direction (θ1) - first-moment spread parameter (r1) - second-moment mean direction (θ2) - second-moment spread parameter (r2) a1,b1,a2,b2 r1 b1 -1 θ1 1 a1

  6. The Directional Spectrum Wave Energy Density Wave Direction θ S(f,θ)=S(f)[a1·cos(θ)+b1·sin(θ) +a2·cos(2θ) +b2·sin(2θ) +a3·cos(3θ)+b3·sin(3θ)+ a4·cos(4θ)+b4·sin(4θ)+………………infinity and beyond]

  7. Data Users & Measurement Accuracy Wave Component Users Dominant Wave Users S(f), Fab5 @ f-peaks θ 1 Generally tolerant of errors. Need a wave component approach to evaluating instrument performance.

  8. Conclusion Let’s talk about the Fab 5 • This is the current state-of-the-art. • This is the bar modern wave instruments should have to clear. • This is the standard emerging technologies should try and achieve before pursuing the Fab 7, the Fab 9….

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