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Swell Variance (cm 2 ) 



Sea Variance (cm 2 ) 



(a) 



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s— s. 



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Swell Variance (cm 2 ) 



Sea Variance (cm 2 ) 



(c) 



(d) 



Figure 20. Scatterplot of infragravity variance against swell (a) and sea (b) 

 variance, and edge wave variance against swell (c) and sea (d) 

 variance (Otlman-Shay 1991) 



determined that at the FRF site, the relationship between infragravity band 

 energy and incident swell energy was linear, suggesting that infragravity energy 

 was predominately from free waves. If the infragravity energy was from bound 

 waves, then the relationship would have been nonlinear, with infragravity energy 

 being proportional to the square of the swell energy. 



The relationship between propagation directions of edge waves and incident 

 swell was also examined in this 8 month data set. ky-f analysis was used to 

 separate up-coast and downcoast propagating edge waves, symmetric about the 

 ky = line, with +k y defining edge waves traveling south, and -ky traveling 

 northward (Figure 21). Incident waves at this time were from a relatively narrow 

 band swell, approaching from approximately 30 deg south of shore normal 



42 



Chapter 4 Field Observations 



