Correlation between infragravity waves, sea, and swell in 8-m depth 



This section presents results from an analysis (Oltman-Shay et al. 1992) of 

 the 8-month SAMSON data set from the FRF 8-m depth array. The analysis 

 separates the wave variance into three frequency bands for infragravity (0.02- 

 0.04 Hz), swell (0.05-0.15 Hz), and sea (0.15-0.3 Hz). The infragravity wave 

 frequency limits were selected, as mentioned above, for isolating edge wave 

 variance from swell and leaky/bound wave variance. Wave variance in this 

 infragravity band is further partitioned, to separate edge and bound wave 

 variance, by summing edge wave variance that lies on edge wave dispersion lines 

 in k-f spectra. In this 8-month data set, 50 percent of the total infragravity 

 variance was from edge waves with as much as 80 percent at times (Figure 19). 



1.0 

 0.8 

 0.6 

 0.4 

 0.2 

 0.0 



Edge Wave / Total \G 



250 300 350 400 450 



Days 



Figure 19. Ratio of edge wave to total infragravity wave variance observed 

 from 1 Sep 1990 to 31 Apr 1991 (Otlman-Shay 1991; Otlman- 

 Shay et al. 1992) 



Infragravity wave variance was shown to have a higher correlation with swell 

 variance than with sea variance (Figures 20a and 20b). Similar correlations are 

 observed for the edge wave variance portion of the infragravity band (Figures 

 20c and 20d) . This is consistent with observations by Elgar et al. (1992) that 

 showed similar correlations at this site and other sites. Their analysis 



Chapter 4 Field Observations 



41 



