channels of a two-axis current meter under the assumption that the biofouling 
or other signal degradation was horizontally isotropic, and because a way to 
determine gain adjustments on individual current meter channels is not known. 
This assumption is important because overcorrecting one current meter channel 
relative to another changes the apparent wave direction at that current meter, 
and degrades the directional estimator. 
To illustrate the temporal behavior of the gains, the time series of the 
gains for each subarray have been plotted. Figure E26 shows the gains from 
the trough subarray, and Figure E27 shows the gains from the crest subarray. 
The results make qualitative sense in that the Marsh-McBirney current meters 
(station 70 in the crest subarray, and all stations in the trough subarray) had 
gains that generally remained within 20 percent of unity, while the Scripps 
open frames (Stations 71-74 in the crest subarray) had gains near unity early in 
the experiment, but drifted high as time evolved, suggesting the influence of 
fouling. Note that all of the gain adjustments were keyed to the spectra from 
the pressure gauges, and, because the pressure gauge depths were modified, 
some noise may have been introduced in the current meter gain adjustments. 
For instance, there appears to be a diel variation in the gains from the trough 
array that is reminiscent of the pressure gauge differences shown in Figure 
E25b. There may be a relationship between these phenomena, but what that 
relationship is, remains uncertain. 
Total water depths 
In an earlier pass through the data, the total water depth, as listed for each 
gauge location, was assumed constant. However, the depths were not constant 
throughout the experiment, and erratic changes in depth occurred after the 
‘energetic events beginning on 10 October. Subsequently, total water depths 
for each gauge site were established by interpolating the bathymetric minigrid 
surveys in both time and space, to obtain a more correct total water depth for 
each gauge location and for each collection. Water depths found in this 
manner are used in analysis and are plotted as time series in Figure E28 
(trough subarray) and Figure E29(crest subarray). When the bar moved 
offshore during the energetic events, shoaling occurred under the crest 
subarray, and deepening occurred under the trough subarray. More consistent 
results overall were obtained when changing depths were used in the analysis. 
Exposed gauges 
Despite efforts to position the gauges so that they remained within the water 
at all tide stages, at some low tide stages, some of the gauges became exposed. 
Because such events add unacceptable noise to the cross-spectral matrix, all 
such cases were eliminated from analysis. These were identified using a 
method similar to that described in the “DELILAH array data analysis” section 
earlier in this appendix. The one difference in this analysis was the use of a 
0.40-m bias in the gauge depth adjustment, and the other analysis determining 
a bias from correlating water levels with a tide gauge (gauge 1). This analysis 
Appendix E Stationary Instrument Data E39 
