One of the first steps in implementing the Prince William Sound Observing System (PWSOS) was to determine what observations were already being made. One such network of existing observation platforms includes the weather buoys and coastal weather stations of the National Data Buoy Center (NDBC). This program of the National Oceanic and Atmospheric Administration has weather buoys throughout the United States, that are used to support the National Weather Service forecasting system and the NOAA marine environmental database.
Recently, the NDBC expanded its services in Alaska, including Prince William Sound. The NDBC already had two weather buoys in the Sound - one at Hinchinbrook Entrance (46061) and one in the central basin at Orca Bay (46060) - as well as one in the Gulf of Alaska at Cape Suckling (46082). The expansion allowed for placement of a new buoy in the northwest Sound at Port Wells (46081) and another at the southern end of Montague Island near Cape Cleare (46076). In addition to these buoys, NDBC maintains three automated weather stations at Bligh Reef (BLIA2), Potato Point (POTA2), and Middle Rock (MRKA2) along the vessel traffic lane leading to the Port of Valdez oil terminal
The weather buoys in PWS are typically three meters in diameter, although larger six meter ones are used for stability in rougher or more open waters such as Hinchinbrook Entrance. The buoys carry an array of instruments that measure wind speed and direction, air pressure, air temperature, and sea surface temperature. They also provide a platform on which other organizations can place instruments. For example, the PWSOS has upgraded each of the three buoys in PWS with instruments that measure ocean temperature, salinity and current velocity.
Current velocity is measured with an Acoustic Doppler Current Profiler (ADCP). An ADCP is an electronic instrument used to measure currents through the entire water column. ADCPs rely on a measure of the Doppler shift to calculate the speed of moving water. The Doppler shift can be experienced regularly in everyday life: think, for example, of the change in sound of passing cars when walking on the side of the road. ADCPs emit a sound at a given frequency and listen to the echo of this sound after it has bounced on small particles naturally present in sea water. The distance between the instrument and the reflecting particles is estimated from the delay between the emission of the sound and the arrival of the echo. Should the echo from a given distance arrive with a higher frequency than the emitted sound, then the volume of water at this distance is moving toward the instrument; should the echo arrive with a lower frequency, then this volume of water is moving away. Larger shifts in frequency indicate larger current speeds.
The measurements made by the NDBC buoys help provide better data on weather patterns in PWS and the Gulf of Alaska. They are the first step toward understanding the variability of weather patterns around PWS, and will allow for more accurate weather forecasting by computer models being developed by the PWSOS.
Data Access
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