Although it is taken for granted, wind is important to people who study weather and climate. Wind speed is a significant factor in making accurate weather forecasts. High winds often indicate change coming in the near future. Instruments for measuring wind speed have been around for ages. These antique instruments were crude and not very accurate. Modern technology allows for much more sophisticated tools, with a level of precision that ancient weather forecasters couldn't have imagined.
The rotational anemometer is a time-honored classic. This anemometer comes in a variety of designs, but the basic principle is the same. Wind blows a freely-rotating instrument around a vertical or horizontal axis. Cups or propellers allow the wind to easily move the instrument. Geometric formulas can then be applied to calculate wind speed based on the rotational speed of the device. Today's digital technologies make this process fairly easy.
The simplest instrument for measuring wind speed is probably the deflection anemometer. The basic design calls for a hinged element that hangs down like a pendulum. Another part of the anemometer is notched with degree marks. The wind blows against the hanging element, creating an angle that can be measured in degrees. A conversion table turns the angle measurement into a corresponding wind-speed value. The deflection anemometer was once cutting edge, but it is primitive by today's standards.
The ultrasonic anemometer is one of the most high tech available. It consists of two or more pairs of sending and receiving nodes, which look like antennae. The sender emits an ultrasonic pulse. At the receiving end, the time required for the pulse to traverse the space between nodes is precisely measured. Using a complex mathematical formula, the ultrasonic anemometer takes the raw data from the receivers and outputs the wind speed. Despite its sophistication, the ultrasonic anemometer is not much larger than an ordinary rotational anemometer.
Doppler radar works by bouncing radar signals off of particles in a cloud, usually rain or hail. The frequency of the signals change depending upon how the particles are moving. The radar can display the relative movement and speed of air inside a storm. Doppler radar is not effective outside of storms, or at providing absolute wind-speed values. It's also not something you can put in your backpack or mount on a fence post. However, a rough estimate of wind speed is critical in understanding the dynamics of severe weather.
- East Lansing Schools Elementary Science: Anemometer
- Teachingonline.org: Anemometer Science Unit
- North Carolina State University: Climate Education for K-12
- Thies Clima: Ultrasonic Anemometer 2D
- NOAA Magazine Online: Weather Radar Development Highlight of National Severe Storms Laboratory's First 40 Years
- Photo Credit Jupiterimages/BananaStock/Getty Images Jupiterimages/Photos.com/Getty Images Ryan McVay/Digital Vision/Getty Images
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