Weather Whys; Anemometers

This is weather wise. Wind direction is fairly easy to observe. You can watch the way the grass bends or in extreme cases the trees. And of course it's easy to tell if the wind is gentle or strong. But to be able to measure rather than just estimate wind speed, meteorologists choose animometers. There are two main kinds of animometers. The oldest is the pressure plate version. It has a rectangular plate of metal hanging from a support with a rudder-like device which keeps the plate perpendicular to the wind direction. The wind then blows the plate upward a certain distance and its angle is related to the wind speed. Often there's a scale mounted beside the plate so you can tell at a glance how fast the wind's blowing. Another more modern instrument for measuring wind speed is called the rotating cup animometer. It has at least three cups attached by small spokes to a hub with a low friction bearing. The assembly of cups is free to spin horizontally and the rate at which it spins is directly

proportional to the wind speed. In older mechanical instruments the hub was connected through some gears to a shaft that was connected to a display somewhat like an ordinary automobile speedometer. Later the animometer and its display were connected only by wires. The hub turns a little electric generator and the display indicates the voltage calibrated in terms of wind speeds. These days that display is likely to be an electronic digital readout. Weatherwise is produced with the assistance of the National Weather Service Forecast Office and the National Severe Storms Laboratory, both in Norman, Oklahoma, and the Cooperative Institute for Mesoscale Meteorological Studies, the Oklahoma Climateological Survey, and the School of Meteorology, all at the University of Oklahoma. For Weatherwise, I'm Drew Barlow.