













0^° 









300 









Constituents 



^ Actual 



D MRS Fundamental 



200 



" 







o MRS 2ci Harmonic 



100 



- 







d< 









1 



1 1 





i 1 1 



Fund; 0.06 

 2d Horm.: 0.12 



0.062 





0.064 



0.124 





0.128 





Frequency 



(Hz) 



6.066 

 0.132 



Figure 14. Phase versus frequency of constituents in Figure 13. 



A further test of MRS analysis applied to actual field records was 

 obtained by recombining constituents to create a synthesized time series. If 

 the MRS constituents are faithful indicators of major components of the field 

 record, the synthesized time series must resemble the field data time series. 

 Plots of actual and synthesized time series are given in Appendix B. 



It is concluded that MRS analysis is indeed a useful tool for identifying 

 and quantifying major constituents in a field wave record. 



3. Wave Groups . 



The MRS technique described previously provides information on the spe- 

 cific frequency constituents which most effectively represent a data time 

 series. A crucial part of this study is to relate this information to wave 

 grouping characteristics of the time series. Since there is no completely 

 satisfactory technique currently available for identifying field wave grouping 

 characteristics, three different techniques were used. All three techniques 

 were set up as well-defined but quasi-objective procedures. 



The first technique is based on the concept of a wave group as a small 

 area of sea surface containing relatively high energy. Groups are identified 

 in a time-series record as sections of the record in which the local variance 

 is high relative to the variance of the whole record. Fluctuations in local 

 variance can provide information on both the intensity and the time scale of 

 wave grouping in the time series. 



Another simple statistic indicative of wave grouping is obtained by defin- 

 ing heights and periods for individual waves in the time series. The auto- 

 correlation between successive wave heights is indicative of any tendency for 



37 



