26
2.2.6 Ocean Winds
Ocean winds, measured up to 320 km.h
−1
during Pacific typhoons, are largely
responsible for surface ocean circulation patterns and their variability. Ocean chemistry and biology are also dependent on these surface winds that influence processes
as diverse as gas exchange and larval dispersal. Anemometers, instruments used to
measure winds, must resist the enormous forces generated by these winds.
Mechanical Rotor Anemometers
In the above context, it is interesting to note that one of the few macro-mechanical
sensors used in ocean observing today is indeed the rotor/vane arrangement still
used for wind measurements. Streamlined torpedo-shaped, freely pivoting bodies,
mounted horizontally on a vertical mast, incorporate forward-mounted helicoidal
rotors and vertical tail vanes (Fig. 2.10).
Instruments designed for ocean deployment make use of the most durable corrosion resistance materials such as ceramic bearings for rotor and mast mount. To avoid
direct electrical contacts or slip-rings, the rotor carries a set of magnets to energize
induction coils within the stationary housing. These current pulses are counted to
derive wind speed. For wind direction, rather than using electronic compasses such
as used in current meters, these instruments rely on precision potentiometers producing an output voltage directly proportional to the horizontal instrument angle. Prior
calibration to a reference compass is required. Such wind gauges are seen aboard
many surface platforms such as shore stations, ODAS buoys, and ships. Rotor instruments incorporating conical side mounted cups also are available.
Fig. 2.10 Mechanical anemometer incorporating pivoting body, helicoidal rotor, and vertical tail
vane
2 Electronic Sensors and Instruments for Coastal Ocean Observing
2.2.6 Ocean Winds
Ocean winds, measured up to 320 km.h
−1
during Pacific typhoons, are largely
responsible for surface ocean circulation patterns and their variability. Ocean chemistry and biology are also dependent on these surface winds that influence processes
as diverse as gas exchange and larval dispersal. Anemometers, instruments used to
measure winds, must resist the enormous forces generated by these winds.
Mechanical Rotor Anemometers
In the above context, it is interesting to note that one of the few macro-mechanical
sensors used in ocean observing today is indeed the rotor/vane arrangement still
used for wind measurements. Streamlined torpedo-shaped, freely pivoting bodies,
mounted horizontally on a vertical mast, incorporate forward-mounted helicoidal
rotors and vertical tail vanes (Fig. 2.10).
Instruments designed for ocean deployment make use of the most durable corrosion resistance materials such as ceramic bearings for rotor and mast mount. To avoid
direct electrical contacts or slip-rings, the rotor carries a set of magnets to energize
induction coils within the stationary housing. These current pulses are counted to
derive wind speed. For wind direction, rather than using electronic compasses such
as used in current meters, these instruments rely on precision potentiometers producing an output voltage directly proportional to the horizontal instrument angle. Prior
calibration to a reference compass is required. Such wind gauges are seen aboard
many surface platforms such as shore stations, ODAS buoys, and ships. Rotor instruments incorporating conical side mounted cups also are available.
Fig. 2.10 Mechanical anemometer incorporating pivoting body, helicoidal rotor, and vertical tail
vane
2 Electronic Sensors and Instruments for Coastal Ocean Observing