second moment about the mean (variance) and then edits the data by checking 

 for "jumps," "spikes," and points exceeding the voltage limit of the gage. A 

 jump is defined as a data value greater than five standard deviations from the 

 previous data value, whereas a spike is a data value more than five standard 

 deviations from the mean. If less than five consecutive jumps or spikes are 

 found, the program linearly interpolates between acceptable data and replaces 

 the erroneous data values. The editing stops if the program finds more than 

 five consecutive jumps or spikes or more than a total of 100 bad points or the 

 variance of the voltage is below 1 x 10- 5 squared volts. The statistics and 

 diagnostics from the analysis are saved. 



35. Sea surface energy spectra are computed from the edited time 

 series. Spectral estimates are computed from smaller data segments obtained 

 by dividing the 4, 096 -point record into several 512 -point segments. The 

 estimates are then ensemble -averaged to produce a more accurate spectrum. 

 These data segments are overlapped by 50 percent (known as the Welch (1967) 

 method) and have been shown to produce improved statistical properties than 

 from nonoverlapped segments. The mean and linear trends are removed from each 

 segment prior to spectral analysis. To reduce sidelobe leakage in the spec- 

 tral estimates, a data window was applied. The first and last 10 percent of 

 data points was multiplied by a cosine bell (Bingham, Godfrey, and Tukey 

 1967). Spectra were computed from each segment with a discreet Fast Fourier 

 Transform and then ensemble -averaged. Sea surface spectra from subsurface 

 pressure gages were obtained by applying the linear wave theory transfer 

 function. 



36. Unless otherwise stated, wave height in this report refers to the 

 energy-based parameter H,,^ defined as four times the zeroth moment wave 

 height of the estimate'd sea surface spectrum (i.e., four times the square root 

 of the variance) computed from the spectrum passband. Energy computations 

 from the spectra are limited to a passband between 0.05 and 0.50 Hz for sur- 

 face gages and between 0.05 Hz and a high frequency cutoff for subsurface 

 gages. This high frequency limit is imposed to eliminate aliased energy and 

 noise measurements from biasing the computation of H^, and is defined as the 

 frequency where the linear theory transfer function is less than 0.1 (spectral 

 values are multiplied by 100 or more) . Smoother and more statistically 

 significant spectral estimates are obtained by band- averaging contiguous 

 spectral components (three components are averaged per band producing a 



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