record is not analyzed. After program editing is completed, the first five 

 moments of the distribution of sea surface elevations are again computed. A 

 cosine bell data window was applied to increase the resolution for the energy- 

 spectrum of the file; use of the data window is discussed by Harris (1974). 

 After application of the data window, the program computes the variance spec- 

 trum (proportional to the energy spectrum) using the FFT procedure. After the 

 data files are analyzed, the results are eliminated for files that are flagged 

 as bad or appear inconsistent with simultaneous observations from nearby gage 

 sites. Frequently the spectrum and/or distribution function of sea surface 

 elevations are examined to determine if the data were acceptable. After the 

 analysis results are edited, monthly summaries of wave heights and periods are 

 generated. 



34. Unless otherwise specified, wave height in this report refers to 



the energy-based parameter H (defined as four times the standard deviation 

 OJ mo 



of the sea surface elevations) . Wave period T is defined as the period as- 



P 

 sociated with the maximum energy in the spectrum which is resolved by parti- 

 tioning the spectrum into frequency bands of equal width and determining the 

 band with the maximum energy density. The period reported is the reciprocal 

 of the center frequency (e.g. T = 1/frequency) of the spectral band. Since 

 the spectral bands are of equal frequency width, namely 0.010742 Hz (i.e. 

 11/1,024 sec), the analysis provides uniform resolution in frequency. How- 

 ever, the resolution in period is not uniform since the period intervals be- 

 come larger for lower frequencies. Because of the combination with the vary- 

 ing width of the period intervals, only a discrete set of period values is 

 possible, as shown below: 



T Not Reported 

 P 











Corresponding 



T 



Associated 





Upp( 



it Limit 



of 



Period 



P 



with 



Band 



Frequency Band 



Lower Limit 



Centi 



=r Frequency 



Number 





Hz 





of Band, sec 

 15.3 



of 



Band, sec 



6 





0.065 







16.8 



7 





0.076 





13.1 





14.2 



8 





0.087 





11.5 





12.3 



9 





0.098 





10.2 





10.9 



10 





0.108 





9.2 





9.8 



15 

 13 



11 



Complete information about the energy contained in all frequency bands can 

 best be obtained by inspecting the full spectrum, examples of which are in- 

 cluded in Appendix B (Volume II) for Gage 625 during storm wave conditions. 



25 



