! Wave height and period (three
sample rate for 34 min every 6 hr,
directional wave spectrum is deter-
except during storms when data
points along the pier);
mined from the FRF's 8-m Direc-
were recorded hourly. Improvements
tional Wave Array composed of 16
! Vertical current profile at 8-m
in data collection computers and
bottom-mounted pressure sensors
(26-ft) depth;
storage capacity allowed for near
arranged in a shore-parallel,
! Water level (four locations and
continuous data collection starting in
shore-normal cross (Long and
National Oceanic and Atmo-
1987. Raw time series, computed
Oltman-Shay 1991). This array was
spheric Administration/National
statistics and spectra are archived
deployed in 1986 and designed by
Ocean Service primary tide sta-
for each sensor and collection
Dr. Joan Oltman-Shay with the
tion);
period.
capability to resolve a unidirectional
wave train to within 5 deg and two
! Water temperature, visibility,
Instrument observations are sup-
wave trains at the same frequency if
salinity (surface and daily profile);
plemented by a daily series of visual
they differ by 15 deg in direction. It
! Wind speed and direction;
observations of parameters like
may be the longest running
cloud cover, air and water visibility,
! Atmospheric pressure, air temper-
high-resolution directional wave
breaker type, alongshore surface
ature, humidity, precipitation;
gauge in the world (Figure 7).
currents, surf zone width, and rip
! Bathymetry (biweekly);
current presence.
In order to maintain real-time
observations, most FRF instruments
! Annual aerial photography; hourly
A NOAA/National Ocean Service
are wired to the main building via a
video imagery
(NOS) primary tide station (number
network of armored cables. Although
865-1370), located at the seaward
Wave measurements have
the data from some sensors are col-
end of the pier collects water-level
always been a primary interest.
lected digitally, most sensors, includ-
data every 6 min. NOS has carefully
Buoy 44014 maintained by the
ing the 8-m Directional Wave Array
monitored and maintained the tide
NOAA/National Data Buoy Center
sensors, provide a continuous
gauge since installation in 1977 and,
(NDBC) provides directional wave
analog voltage output that is digi-
as a result, an excellent record of
measurements 94 km (58 mi) from
tized at the computer. A Global
sea level rise, and water-level varia-
shore in 47-m (150-ft) water depth,
Positioning System (GPS) time-
tion, has been obtained. During the
near the edge of the continental
server controls the digitization so
period, NOS converted from their
shelf. A Datawell Directional
that the phase relationship between
traditional punch paper tape measur-
Waverider Buoy measures
sensors can be precisely measured.
ing system to their next generation
nonbreaking wave conditions 4 km
Originally, data from all analog sen-
water-level station, based largely on
(2.5 mi) offshore in 16 m (52 ft) of
sors were recorded at a 2-Hz
development and performance tests
water. Further inshore, the full
Figure 7. Directional wave spectra collected at the 8-m Directional Wave Array during the passage of Hurricane Bonnie.
These data show the significant and rapid changes in the distribution of wave energy reaching the beach
17
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