Figure 6-1.-Aerial photo of sea waves.
in appearance than sea waves. Figure 6-2
illustrates typical swell wave conditions.
PROPERTIES OF WAVES
All waves have the following properties in
common:
Amplitude. The amplitude of a wave is the
maximum vertical displacement of a particle of the
wave from its rest position. In the case of ocean
waves, the rest position is sea level.
Wave Height (H). Wave height is the vertical
distance from the top of the crest to the bottom of
the trough. Wave height is measured in feet. Four
values for wave height are determined and
forecast. They are:
1. Havg (the average height of the waves).
This average includes all the waves from
the smallest ripple to the largest wave.
2. Hsig or H1/3 (the average height of the
highest one-third of all waves). This
significant height of waves seems to
represent the wave heights better than
the other values, and this value will be
used most often for this reason
3. H1/10 (the average height of the highest
one-tenth of all waves). H1/10 is used to
indicate the extreme roughness of the
sea.
4. Hmax - high wave.
Period (T). The period of a wave is the time
interval between successive wave crests, and it
is measured in seconds.
Frequency (f). The frequency of waves is the
number of waves passing a given point during
1 second. It is the reciprocal of the period. In
general, the lower the frequency, the longer the
wave period; the larger the frequency, the
shorter the wave period.
6-2
