Real-Time Buoy Directional Wave Measurements for
Driving Surf Zone Numerical Computer Models
Marshall D. Earle
Tactical Oceanographic Warfare Support Program Office
Naval Research Laboratory, Stennis Space Center
The objectives were to make real-time directional wave measurements outside the surf
zone using small easily-deployed buoys, and to determine whether such data can drive an
automated surf zone numerical computer model to accurately "nowcast" surf conditions
including breaking characteristics and longshore currents.
Measurements taken during DUCK94 were also used determine the value of using such buoys to monitor incident wave conditions during coastal
processes studies in general.
Versions of air-deployed expendable sonobuoy-sized wave measurement buoys that are
being developed for the U.S. Navy will be moored immediately outside the surf zone. One buoy
will be deployed during August, two during October, the main period of interest when waves are
typically higher. A spare buoy should be available each month and could be deployed during an
event of particular interest. Deployments will be from surface vessels rather than aircraft.
Buoys are cylinder-shaped (approximately 12 cm in diameter and 90 cm long) with an inflated
floatation collar. Meteorological data and results of onboard wave data analysis are relayed to
shore via ARGOS satellite. Available information includes air temperature, sea temperature,
barometric pressure, nondirectional wave spectra, and directional wave spectra parameters.
Measured wave conditions will drive a surf zone numerical computer model operating on a
PC-type computer or workstation.
During October, an additional wave measurement buoy may be deployed by commercial
vessel further offshore (several km) in coordination with ambient noise measurements and
NASA aircraft radar altimeter directional wave measurements made by other experiments. At
that time, an Expendable Oceanographic Mooring (XMOOR) being developed by NRL Stennis
Space Center (J. Boyd) may also be tested at a location away from other moored sensors to avoid
physical interference. XMOOR would provide atmospheric pressure, air temperature, sea
surface and near bottom temperatures, thermistor string temperatures (5 m spacing), conductivity
(surface, mid-depth, near bottom), and subsurface pressures (mid-depth and near bottom) using
ARGOS satellite and radio frequency data transmission.
For a list of addresses of the investigators involved in Duck
94 click here.