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Handbook No. 1
Can You Describe the Moored Buoys?
Moored Buoy Hull Characteristics -- Moored buoys are the weather sentinels of the sea. They are deployed in the coastal and offshore waters from the western Atlantic to the Pacific Ocean around Hawaii, and from the Bering Sea to the South Pacific. NDBC's moored buoys measure and transmit barometric pressure; wind direction, speed, and gust; air and sea temperature; and wave energy spectra from which significant wave height, dominant wave period, and average wave period are derived. Even the direction of wave propagation is measured on many moored buoys.
NDBC's fleet of moored buoys includes 4 types: 3-m, 10-m, 12-m discus hulls, and 6-m boat-shaped (NOMAD) hulls. The choice of hull type used usually depends on its intended deployment location and measurement requirements. To assure optimum performance, a specific mooring design is produced based on hull type, location, and water depth. For example, a smaller buoy in shallow coastal waters may be moored using an all-chain mooring. On the other hand, a large discus buoy deployed in the deep ocean may require a combination of chain, nylon, and buoyant polypropylene materials designed for many years of service. Some deep ocean moorings have operated without failure for over 10 years.
In addition to their use in operational forecasting, warnings, and atmospheric models, moored buoy data are used for scientific and research programs, emergency response to chemical spills, legal proceedings, and engineering design.
The following is a more detailed description of the different types of buoy hulls that are used by NDBC.
Discus buoys -- Discus buoys have circular hulls. NDBC's operational discus buoys are designed in three sizes: 12-meters, 10-meters, and 3-meters. The steel-hulled, 12-meter discus buoys are more sturdy in rough weather than the smaller, steel-hulled 10-meter discus buoy, but are more costly to maintain. The 10-meter buoy has been known to capsize in certain environmental conditions and the overall motion of the buoy is more lively than that of the 12-meter buoy. Due to their size, the 10-meter and the 12-meter buoys generally have to be towed behind a Coast Guard Cutter to their appropriate locations.
The aluminum-hulled, 3-meter discus is very cost-effective but does not offer long-term survivability that the larger discus hulls provide. The transportability of the 3-meter buoy is much improved over that of the larger discus buoys. It easily can be carried on a flat-bed trailer. Since it is constructed of aluminum, it is less likely to corrode, and compass measurements are not affected.
NOMAD buoys -- The 6-meter NOMAD is an aluminum-hulled, boat-shaped buoy which provides relatively high cost effectiveness and excellent long-term survivability in severe seas. These buoys are highly directional and have a quick rotational response. There have been no known capsizings of 6-meter NOMAD hulls. The relatively small size of the NOMAD allows for superb transportability via flatbed trailer, rail, or ship. Like the 3-meter discus, they are less likely to corrode and the magnetic effects on the compass are slight.
An updated list of deployed buoys is available. Included in the description are their exact lat/lon location, the water depth, and the watch radius of the mooring. A description of sensor heights is also available.