monochromatic waves. Therefore, care should be exercised in analyzing the raw
time-series data in either time or frequency domain. It may be appropriate for the
user of the data to view the data carefully and select later segments of the data
stream for comparison to numerical model estimates.
Table 3
Calculated Wave Parameters from Down-crossing Analysis
Parameter Name
Description
ETABAR
Average water level
ETARMS
Root-mean-squared water level
ETAMAX
Maximum water-surface elevation
ETASD
Standard deviation of water level
RHOHH
Correlation between wave heights
RHOHT
Correlation between heights and periods
HMIN
Smallest wave height
HMAX
Largest wave height
HBAR
Average wave height
H 1/3
Significant wave height, average of highest 33 percent of
wave heights
H 1/10
Average of highest 10 percent of wave heights
H 1/20
Average of highest 5 percent of wave heights
H 1/100
Average of highest 1 percent of wave heights
TBAR
Average wave period
T 1/3
Significant wave period, average period of highest 33 percent
of waves
T 1/10
Average wave period of highest 10 percent of wave heights
T 1/20
Average wave period of highest 5 percent of wave heights
T 1/100
Average wave period of highest 1 percent of wave heights
For Rayleigh distribution of wave heights, alpha = 2 and beta
WEIBULL ALPHA
= 0.5. Truncation of higher wave heights by breaking
WEIBULL BETA
increases alpha.
NO. OF WAVES
Number of waves in record.
H (P=0.5)
Median wave height (exceeded 50 percent)
T (P=0.5)
Median wave period (exceeded 50 percent)
21
Chapter 3 Measurement Procedures and Data Analysis
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