• Anemometers measure wind speed and determine wind direction. Using these sets of data, meteorologists can calculate wind pressure. Wind pressure is the force exerted on a structure by the wind.

Weather Vane
Weather vanes are instruments that show the direction of the wind. Although they provide information about where wind is blowing, they are mostly decorative and do not give the same information about wind speed as anemometers.

Anemometers in Space
NASA is considering a mission to Venus that would use an anemometer to measure wind speed on that planet. Scientists hope the anemometer and other instruments will paint a better picture of Venus' surface and atmosphere.

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 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.

• Term Part of Speech Definition Encyclopedic Entry
aerodynamics Noun

the study of how air moves.

aerospace Noun

business concerned with the manufacturing and operation of vehicles that fly in and above Earth's atmosphere.

air Noun

layer of gases surrounding Earth.

Encyclopedic Entry: air
air pressure Noun

force pressed on an object by air or atmosphere.

anemometer Noun

a device that measures wind speed.

Encyclopedic Entry: anemometer
Arctic Noun

region at Earth's extreme north, encompassed by the Arctic Circle.

Encyclopedic Entry: Arctic
barometer Noun

an instrument that measures atmospheric pressure.

Encyclopedic Entry: barometer
breeze Noun

light wind or air current.

calculate Verb

to reach a conclusion by mathematical or logical methods.

climatologist Noun

person who studies long-term patterns in weather.

determine Verb

to decide.

engineer Noun

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 equator.

forecast Verb

to predict, especially the weather.

very cold.

gust Noun

sudden, strong wind.

left-right direction or parallel to the Earth and the horizon.

hot-wire anemometer Noun

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 Noun

tool.

laser Noun

(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.

lull Noun

calm or still wind.

meteorologist Noun

person who studies patterns and changes in Earth's atmosphere.

particle Noun

small piece of material.

physicist Noun

person who studies the relationship between matter, energy, motion, and force.

pilot Noun

person who steers a ship or aircraft.

region Noun

any area on Earth with one or more common characteristics. Regions are the basic units of geography.

Encyclopedic Entry: region
rotate Verb

to turn around a center point or axis.

alike or resembling.

sound wave Noun

wave of air pressure producing sound.

spacecraft Noun

vehicle designed for travel outside Earth's atmosphere.

storm Noun

severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

temperature Noun

degree of hotness or coldness measured by a thermometer with a numerical scale.

Encyclopedic Entry: temperature
tube anemometer Noun

instrument that measures wind speed by comparing air pressure outside a tube to air pressure inside it.

velocity Noun

measurement of the rate and direction of change in the position of an object.

vertical Noun

up-down direction, or at a right angle to Earth and the horizon.

weather pattern Noun

repeating or predictable changes in the Earth's atmosphere, such as winds, precipitation, and temperatures.

weather station Noun

area with tools and equipment for measuring changes in the atmosphere.

windmill Noun

instrument that generates power from the force of wind rotating large blades.

wind speed Noun

force and velocity of wind.

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