rubber diaphragms. A Teflon scouring pad dipped in anti fouling paint 

 separates the rubber diaphragm from the end of the package which admits 

 the seawater pressure. The instrument is mounted vertically on a tri- 

 pod (Fig. 6) . The signals from the pressure transducers are brought by 

 cables to a recording and transmitting station onshore. 



2, Data Collection . 



The array went into operation on 27 March 1970. The water pressure 

 at the five gages was registered continuously at a rate of four times a 

 second on digital magnetic tape. Difficulties experienced during the 

 first year with individual sensors were mostly of short duration and 

 were presumed to be due to biological activity. However, major diffi- 

 culties were experienced with the recording system, and on 16 March 1971 

 the recorder was disconnected at Pt. Mugu and transferred to the CERC 

 laboratory, then located in Washington, D.C. Recording from all five 

 gages was reinitiated at CERC on 9 April 1971. Records were obtained 

 continuously until 3 January 1972 when the recorder failed. During this 

 period much of the data were useless because of an unacceptable level of 

 high-frequency noise. The source of the noise was difficult to locate 

 and was not eliminated from the signal until shortly before the failure 

 of the recorder in January. Since 2 February 1972, records from three 

 of the five gages at Pt. Mugu have been included in the time-shared 

 recording of waves from ecist and gulf coast wave stations (Peacock, 

 1974). In 1972, data were recorded for 20 minutes out of each hour; 

 since February 1973, data have been recorded for 20 minutes out of each 

 2-hour interval. 



II. FIELD DATA ANALYSIS 



The five gages in the array provided uninterrupted data for most of 

 the first year of operation. Eight daily observations, each consisting 

 of simultaneous 20-minute records from the five gages, were processed 

 from these data. The observations had starting times within 1.5 hours 

 of the weather synoptic times (0100, 0400, 0700, 1000, 1300, 1600, and 

 1900 hours P.s.t.). The potential energy in the wave field is propor- 

 tional to the variance of the time history of sea-surface elevation at 

 a fixed location (Kinsman, 1965). For most conditions, the standard 

 deviation of the surface displacement is one- fourth of the significant 

 wave height. The standard deviation of the pressure at a fixed depth is 

 roughly proportional to the wave height and may also serve as a measure 

 of the wave height. 



The standard deviation of the recorded pressure was computed from the 

 records of each of the five gages for eight records each day. The stand- 

 ard deviation of the record from each gage was compared with the average 

 of the five gages. If the standard deviation from any gage differed from 

 the average by more than 20 percent, the record from that gage was deleted 

 and the average recomputed from the remaining gages . A comparison of the 

 individual standard deviations from the mean for that time period is shown 

 in Table 1. 



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