Print this pageAbstract: Polymodal Deep-Water 
Wave
-Rider Buoy Data
TANNER, W. F.
Florida State Univ., Tallahassee,
FL
Deep-water wave-rider buoys report near-realtime measurements
of wave period and wave height off of the shores of the U.S. These records
are largely polymodal, commonly with 2 to 4 modes, in some instances with
five, six or seven. This information cannot be obtained by observation
of breaker lines on the coast itself after shoaling has already modified
open-sea characteristics.
Because of this polymodality, calculations of mean period & mean
height are not very useful Instead, one needs the modes. The mean may indicate
a wave which does not exist in the study area. The significant wave is
also suspect; in addition to a poor and arbitrary definition, it probably
does not represent any mode at all.
In simulation of shoaling of open-sea waves by computer means, one needs
the first mode (the longest period, the highest wave). The shoaling process
may increase the polymodality, so that waves obtained at or immediately
prior to breaking may be different from what was seen in deep water. In
addition, the shoaling process may produce a "zero component" (important
time interval on the coast when there are no waves at all; Tanner 1977).
Finally, shoaling may cause truncation of a few modes so that the near-shore
wave record may depart still differently from deepsea data.
The new deep-water wave
data do not match well with wind and fetch.
This may be due to the presence of Langmuir circulation, which provides
an important water surface motion that is due to neither waves nor currents.
There are also problems with continuity of data from hour to hour, but
these may be relatively minor.
AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas