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1 Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore ANEMO METER For the complete encyclopedic entry with media resources, visit: An anemometer is an instrument that measures wind speed and wind pressure. Anemometers are important tools for meteorologists, who study weather patterns. They are also important to the work of physicists, who study the way air moves. The most common type of anemometer has three or four cups attached to horizontal arms. The arms are attached to a vertical rod. As the wind blows, the cups rotate, making the rod spin. The stronger the wind blows, the faster the rod spins. The anemometer counts the number of rotations, or turns, which is used to calculate wind speed. Because wind speeds are not consistent there are gusts and lulls wind speed is usually averaged over a short period of time. A similar type of anemometer counts the revolutions made by windmill-style blades. The rod of windmill anemometers rotates horizontally. Other anemometers calculate wind speed in different ways. A hot-wire anemometer takes advantage of the fact that air cools a heated object when it flows over it. (That is why a breeze feels refreshing on a hot day.) In a hot-wire anemometer, an electrically heated, thin wire is placed in the wind. The amount of power needed to keep the wire hot is used to calculate the wind speed. The higher the wind speed, the more power is required to keep the wire at a constant temperature. Wind speed can also be determined by measuring air pressure. (Air pressure itself is measured by an instrument called a barometer.) A tube anemometer uses air pressure to determine the wind pressure, or speed. A tube 1 of 5

2 anemometer measures the air pressure inside a glass tube that is closed at one end. By comparing the air pressure inside the tube to the air pressure outside the tube, wind speed can be calculated. Other anemometers work by measuring the speed of sound waves or by shining laser beams on tiny particles in the wind and measuring their effect. Uses of Anemometers Anemometers are used at almost all weather stations, from the frigid Arctic to warm equatorial regions. Wind speed helps indicate a change in weather patterns, such as an approaching storm, which is important for pilots, engineers, and climatologists. Aerospace engineers and physicists often use laser anemometers. This type of anemometer is used in velocity experiments. Velocity is the measurement of the rate and direction of change in the position of an object. Laser anemometers calculate the wind speed around cars, airplanes, and spacecraft, for instance. Anemometers help engineers make these vehicles more aerodynamic. Vocabulary Term aerodynamics aerospace the study of how air moves. business concerned with the manufacturing and operation of vehicles that fly in and above Earth's atmosphere. air layer of gases surrounding Earth. air pressure force pressed on an object by air or atmosphere. anemometer a device that measures wind speed. 2 of 5

3 Arctic Term region at Earth's extreme north, encompassed by the Arctic Circle. barometer an instrument that measures atmospheric pressure. breeze light wind or air current. calculate verb climatologist consistent to reach a conclusion by mathematical or logical methods. person who studies long-term patterns in weather. adjectivemaintaining a steady, reliable quality. determine verb to decide. engineer equatorial person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer). having to do with the equator or the area around the adjective equator. forecast verb to predict, especially the weather. frigid adjectivevery cold. gust sudden, strong wind. horizontal hot-wire anemometer left-right direction or parallel to the Earth and the adjective horizon. instrument that measures wind speed by measuring the amount of power needed to keep a hot wire at a consistent temperature. indicate verb to display or show. instrument tool. laser lull calm or still wind. meteorologist (acronym for light amplification by stimulated emission of radiation) an instrument that emits a thin beam of light that does not fade over long distances. person who studies patterns and changes in Earth's atmosphere. 3 of 5

4 Term particle small piece of material. physicist person who studies the relationship between matter, energy, motion, and force. pilot person who steers a ship or aircraft. region any area on Earth with one or more common characteristics. Regions are the basic units of geography. rotate verb to turn around a center point or axis. similar adjectivealike or resembling. sound wave wave of air pressure producing sound. spacecraft vehicle designed for travel outside Earth's atmosphere. storm severe weather indicating a disturbed state of the atmosphere resulting from uplifted air. temperature degree of hotness or coldness measured by a thermometer with a numerical scale. tube anemometer instrument that measures wind speed by comparing air pressure outside a tube to air pressure inside it. velocity measurement of the rate and direction of change in the position of an object. vertical up-down direction, or at a right angle to Earth and the horizon. repeating or predictable changes in the Earth's weather atmosphere, such as winds, precipitation, and pattern temperatures. weather area with tools and equipment for measuring changes in station the atmosphere. windmill instrument that generates power from the force of wind rotating large blades. wind speed force and velocity of wind. Articles & Profiles National Geographic Science: Wind 4 of 5

5 California Energy Commission: Make an Anemometer Worksheets & Handouts Department of Energy: Wind Powering America Native American Anemometer Loan Program National Geographic Society. All rights reserved. 5 of 5