temperature is above 10° C. At least one cleaning and painting with antifoul- 

 ant paint during the summer reduces the fouling problem. 



28. Ribe (1981) presents three correction factors to use to increase 

 wave measurement accuracy. These factors are (a) the Datawell-specif ied de- 

 crease in electronic sensitivity as a function of oscillation period, (b) a 

 difference error based on deviations from (a) found during NOAA's calibra- 

 tions, and (c) a temperature-dependent adjustment of the sensitivity due to 



an unknown chemical reaction in the conducting fluid surrounding the Waverider 

 accelerometer . These corrections and their application are discussed below. 



29. Datawell-predicted decrease in sensitivity (DW) . Waverider buoy 

 sensitivity /A/ for the buoy electronics decreases with increasing period 

 T of sinusoidal vertical motion according to Datawell as follows: 



/A/ = 



1 + 



4"l ^/2 



where To = 30.8 seconds is a characteristics period provided by Datawell. 

 This sensitivity decrease results in amplitude errors of less than 3 percent 

 for oscillation (wave) periods less than 15 seconds. Figure 4 presents curves 

 for (a) (DW) = /A/-1 , the Datawell-predicted sensitivity decrease error, and 

 (b) the actual sensitivity decrease error obtained from predeployment buoy 

 calibrations. Note the actual sensitivity does not follow the Datawell 

 relationship (Equation 1) given above. 



30. Difference error (d) . Ribe (1981) presents a least-mean-squares 

 second-order polynomial of the form shown below in period T for a "best- 

 estimate" difference error d between the Datawell-predicted decrease in 

 sensitivity and that found from the actual buoy calibrations: 



d = a + (a, X T) + (a_ X T^) (2) 



o 1 z 



In Table 2, DW and d are tabulated as functions of T for each of the FRF 

 buoys . 



31. Temperature-related error. It was determined that for some un- 

 known number of Waveriders the sensitivity was drifting downward, possibly 

 since manufacture, and averaging about 1 percent per year. Sensitivity loss 

 from some unknown chemical reaction was related to increases in electrical 



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