ranks the selected frequencies which explain the maximum amount of variance in 

 the data time series. The first frequency is the one most highly correlated 

 with the data time series. The second frequency, together with the first 

 frequency, explains the maximum amount of variance in the data time series. 

 The third frequency, along with the first and second frequencies, is selected 

 to make the maximum improvement. The selection process is continued until a 

 desired number of frequencies have been selected or until a desired fraction 

 of the variance has been explained. Amplitudes and phases for each selected 

 frequency are recomputed each time a new frequency is selected. 



The development of systemmatic screening procedures and application to 

 meteorological problems are briefly reviewed by Harris (1962). The procedures 

 have been adapted for use with ocean wave records (D.L. Harris, Research 

 Scientist, University of Florida, personal communication). A detailed 

 description of the technique used in this study is given in Appendix A. 



The MRS technique is well suited for use with a high-speed digital com- 

 puter. However, the extensive manipulations and memory requirements involved 

 in MRS make it impractical to specify more than about 100 different frequen- 

 cies. This number is far short of the number of frequencies necessary to 

 obtain a detailed resolution in a field data record of unknown frequency 

 composition. 



For this study, field wave records can be efficiently analyzed by using a 

 combination of both MRS and FFT techniques . The FFT analysis with no data 

 window is applied first to a record approximately 15 minutes long to identify 

 the general range of frequencies encompassing the high-energy concentrations. 

 Then the MRS analysis is used with a coarse-toothed comb of 88 equispaced 

 frequencies covering the high-energy range. This configuration was modified 

 slightly for analysis of the Columbia Light records in that only 60 equispaced 

 frequencies were used to span the high-energy range and the additional 28 

 frequencies were used to cover a range at twice the frequency of the high- 

 energy range. The frequency spacing ranged from 0.0004 hertz for Columbia 

 Light to 0.002 hertz for South Pass. A second MRS analysis used a series of 

 fine-toothed combs centered on the frequencies ranked highest in the first MRS 

 analysis. A third MRS analysis was used when needed to obtain an accuracy of 

 between 0.0001 and 0.0002 hertz. The MRS was applied to a 1,024-second record 

 at South Haven, a 512-second record at Columbia Light, and a 600-second record 

 at South Pass, although the analysis procedures impose no inherent restric- 

 tions on record length. 



The MRS program is set up to print a summary of selected constituents at 

 each step in the analysis. Thus, each time a new frequency constituent, oj- , 

 is selected and the corresponding Q^ and a^^ in equation (A-13) in Appendix 

 A have been computed, a printed display of A^^ and tj)^ in equation (A-14) 

 and ojj is provided for all u- selected thus far. The display was used to 

 subjectively decide how many constituents should be retained from each analy- 

 sis, as follows. In the initial part of each run the amplitude and phase of 

 each selected constituent changed very little as constituents were added. 

 However, eventually a constituent was added which was nearly identical in 



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