A Guide to the Tools Used to Measure the Weather World

A tornado forming with dramatic lightning in Texas
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Weather instruments are devices used by atmospheric scientists to sample the state of the atmosphere, or what it's doing, at a given time. Unlike chemists, biologists, and physicists, meteorologists don't use these instruments in a lab. They're used in the field, placed outdoors as a suite of sensors which, together, provide a complete picture of weather conditions. Below is a beginner's list of the basic weather instruments found in weather stations and what each one measures.

Anemometer

A small, backyard personal weather anemometer

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Anemometers are devices used to measure winds. While the basic concept was developed by Italian artist Leon Battista Alberti around 1450, the cup-anemometer wasn't perfected until the 1900s. Today, two kinds of anemometers are most often used:

  • The three-cup anemometer determines wind speed based on how fast the cup wheel spins and wind direction from the cyclical changes in ​cup wheel speed.
  • Vane anemometers have propellers on one end to measure wind speed and tails on the other for determining wind direction.

Barometer

A barometer surrounded by autumn leaves

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A barometer is a weather instrument used to measure air pressure. Of the two main types of barometers, mercury and aneroid, aneroid are more widely used. Digital barometers, which use electrical transponders, are used in most official weather stations. Italian physicist Evangelista Torricelli is credited with inventing the barometer in 1643. 

Thermometer

A wooden thermometer lying on a dark surface

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Thermometers, one of the most widely recognized weather instruments, are tools used to measure ​ambient air temperature. The SI (international) unit of temperature is degrees Celsius, but in the U.S. we record temperatures in degrees Fahrenheit.

Hygrometer

The dial on a hygrometer indicates slightly dry conditions

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First invented in 1755 by Swiss "renaissance man" Johann Heinrich Lambert, the hygrometer is a tool that measures humidity, or moisture content in the air.

Hygrometers come in all types:

  • Hair tension hygrometers relate the change in length of a human or animal hair (which has an affinity to absorbing water) to a change in humidity.
  • Sling psychrometers use a set of two thermometers (one dry and one moistened with water) are spun in the air.
  • Of course, as is true of most modern weather instruments used today, the digital hygrometer is preferred. Its electronic sensors change in proportion to the level of moisture in the air.

Rain Gauge

A half full rain gauge in a blooming garden

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If you have a rain gauge at your school, home, or office you know what it measures: liquid precipitation. While a number of rain gauge models exist, the most widely used include standard rain gauges and tipping-bucket rain gauges (so-called because it sits on a seesaw-like container that tips over and empties out whenever a certain amount of precipitation falls into it).

Although the first known rainfall records date back to the Ancient Greeks and BCE 500, the first standardized rain gauge wasn't developed and used until 1441 by the Joseon Dynasty of Korea. Any way you slice it, the rain gauge is still among the oldest weather instruments in existence.

Weather Balloon

A tethered weather balloon for testing national air quality slowly rises into the sky

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A weather balloon or sounding is a sort of mobile weather station in that it carries instruments into the upper air in able to record observations of weather variables (like atmospheric pressure, temperature, humidity, and winds), then sends back this data during its suborbital flight. It is comprised of a 6-foot-wide helium- or hydrogen-filled latex balloon, a payload package (radiosonde) that encases the instruments, and a parachute that floats the radiosonde back to the ground so that it can be found, fixed, and reused. Weather balloons are launched at over 500 locations worldwide twice per day, usually at 00 Z and 12 Z.

Weather Satellites

A weather satellite for observing powerful thunderstorms and tornadoes from space orbits the planet

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Weather satellites are used to view and gather data about Earth's weather and climate. Meteorological satellites see clouds, wildfires, snow cover, and ocean temperatures. Just like rooftop or mountain top views offer a wider view of your surroundings, a weather satellite's position several hundred to thousands of miles above Earth's surface allows observation of weather across large areas. This extended view also helps meteorologists spot weather systems and patterns hours to days before being detected by surface observing instruments, like weather radar.

Weather Radar

A weather radar with a blue sky and a plane in the background

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Weather radar is an essential weather instrument used to locate precipitation, calculate its motion, and estimate its type (rain, snow, or hail) and intensity (light or heavy).

First used during World War II as a defense mechanism, radar was identified as a potential scientific tool when military personnel happened to notice "noise" from precipitation on their radar displays. Today, radar is an essential tool for forecasting precipitation associated with thunderstorms, hurricanes, and winter storms.

In 2013, the National Weather Service began upgrading its Doppler radars with dual polarization technology. These "dual-pol" radars send and receive horizontal and vertical pulses (conventional radar only sends out horizontal) which gives forecasters a much clearer, two-dimensional picture of what's out there, be it rain, hail, smoke, or flying objects.

Your Eyes

A woman shades her eyes from bright sunlight to see into the distance

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There's one very important weather observing instrument we haven't mentioned yet: the human senses!

Weather instruments are necessary too, but they can never replace human expertise and interpretation. No matter what your weather app, indoor-outdoor weather station records, or access to high-end equipment, never forget to verify it against what you observe and experience in "real life" outside your window and door.

In-Situ vs. Remote Sensing

Each of the above weather instruments uses either the in-situ or remote sensing method of measuring. Translated as "in place," in-situ measurements are those taken at the point of interest (your local airport or backyard). In contrast, remote sensors collect data about the atmosphere from some distance away.