Weather forecast instruments are a vital component in our application of science and technology in an attempt to predict future conditions of the atmosphere for a given time and location. Whilst not 100% accurate, it definitely has come a long way over the millennia.
These 26 weather forecast instruments and inventions have helped define and improve how we predict the weather today. This list is far from exhaustive and is in no particular order.
1. Barometer: weighing the air since the 1600s
The barometer is one of the most important instruments in weather forecasting. It is used, as the name suggests, to measure localized atmospheric air pressure.
Evangelista Torricelli is widely credited with the invention of the barometer in the mid 17th Century. But historical documentation also indicates that Gasparo Berti, another Italian scientist, built a working barometer by accident between 1640 and 1643.
Berti was a friend of Galileo who in turn was the mentor of Torricelli. Berti could not explain how his 'barometer' worked, invoking a theory that the vacuum in some way held the water level in the tube and asked Galileo for advice.
If this is true, Torricelli later made the connection between atmospheric pressure and the phenomenon described by Gasparo Berti in his apparatus.
He would later write:
"We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight".
Torricelli also later discovered he could replicate the phenomenon in 'miniature' using denser fluids like mercury.
Traditionally, barometers came forms such as:
- Water (Goethe)
- Mercury and
- Aneroid (later invented in 1844 by Lucien Vidi).
Analog forms are rarely used for official weather prediction today, having largely been replaced with digital ones. Digital barometers use electrical transponders, instead of liquids in a vacuum, to detect atmospheric pressure and are the most widely used form in official weather stations today.
Air pressure, when combined with wind observations has been used to predict, fairly accurately, short-term weather forecasts since the later 19th Century.
2. The anemometer measures wind speeds
Wind speeds can be accurately measured using devices called anemometers. They were first developed by Italian artist Leon Battista Alberti in 1450 but were perfected much later in the 20th Century.
They are a common instrument often found on weather stations. Their design has changed very little since the 15th Century.
The most easily recognizable forms used in weather forecasting include:
- Cup anemometers.
- Vane anemometers.
The first determines wind speed based on how fast the cup wheel spins. Improvements made to the design in 1991 by Derek Weston, also allows them to determine wind directions from the cyclical changes in the cup wheel speed.
Although simple in theory, other factors need to be factored in before determining true wind speeds. For instance, turbulence from the device itself and friction from the mount point needs to be accounted for.
A vane anemometer, on the other hand, combines a propeller and a tail on the same axis to obtain accurate and precise wind speed and direction measurements from the same instrument. Wind speed is determined using a rev counter which is then converted to wind speed.
There are also other forms of anemometer ranging from hot-wire anemometers (the most popular constant-temperature devices), Laser Doppler anemometers, ultrasonic anemometers, and ping-pong ball anemometers (though generally confined to middle-school experiments).
3. Radar can detect airplanes and rainfall
Today, radar forms an integral part of any weather instrumentation and is used, primarily, to locate precipitation, track it and estimate its type (snow, rain, etc) and intensity. Radar can also be used to forecast precipitation associated with thunderstorms, hurricanes, and winter storms.
Radar was initially developed during the Second World War as a means of detecting and tracking enemy aircraft. Personnel soon noticed "noise" or "echoes" on their displays from precipitation which revealed a potential peacetime application for the technology.
Shortly after the conclusion of the war, surplus radar equipment was repurposed on weather stations.
Modern stations use pulse-Doppler Radar that is actually capable of detecting the motion of rain droplets as well as the intensity of the precipitation. They typically use dual-polarization radar that sends and receives vertical and horizontal pulses.
This gives meteorologists a much clearer appreciation of the multi-dimensional situation at any one time.
4. Rain gauges have been used to measure rain since 500 BC
Rain gauges are pretty simple instruments used to directly measure the amount of liquid precipitation in one location over a period of time. They are vital instruments for meteorologists and hydrologists alike.
Rain gauges are one of the world's oldest and most basic weather instruments around. Some of the first recorded apparatus dates back to Ancient Greece around 500 BC. Other records indicate that people living in India also started measuring rainfall in around 400 BC.
The first standardized rain gauge appears to have been developed in 1441 AD in the Joseon Dynasty of Korea. The first "tipping bucket" form of rain gauge was developed by Sir Christopher Wren in 1662.
Richard Towneley is the first person to systematically measure and record rainfall over a period of 15 years from 1677 to 1694. He later inspired other scientists of the age to follow suit, eventually leading the pioneering work of George James Symons (one of the first official Meteorologists who founded the British Rainfall Organisation).
Most modern rain gauges generally measure the precipitation in millimeters in height collected on each square meter during a certain period, equivalent to liters per square meter.
These can be simple collection systems that are later visited by meteorologists to assess rainfall or automated to gather data in situ.
5. Weather balloons take weather forecasting to new heights
Weather or sounding balloons are effectively mobile weather stations that carry scientific instruments into the upper atmosphere. They tend to be equipped with suites of sensors to measure weather variables like atmospheric pressure, temperature, and humidity.
This information is relayed to ground-based receiver stations to be stored and analyzed.
Other information, like wind data, can be obtained by tracking the balloon's position using radar, radio direction finding or installing GPS systems on each balloon. Other instruments are encased in small, parachute-equipped though often expendable, payloads called radiosondes.
Each balloon tends to comprise a large, often up to 6 ft (1.8 meters) wide, helium or hydrogen-filled latex balloon. The balloons then carry an instrument payload package that encases and protects the more sensitive instruments during its flight.
Leon Teisserence de Bort, a French meteorologist, was one of the first people to use weather balloons. He launched hundreds of them during 1896 which led to his discovery of the troposphere and stratosphere.
Some balloons, called transosondes, are designed to stay aloft for long periods of time. They were initially devised to help monitor radioactive debris from atomic fallout during the 1950s.
6. The humble thermometer is a vital piece of kit
Another basic yet fundamental instrument used for weather forecasting is the humble thermometer. They are generally used for measuring the ambient temperature of the air.
The device is pretty simple in design and consists of the following important components.
- A temperature sensor. This includes a bulb of mercury in traditional analog thermometers or a digital sensor in modern infrared thermometers
- A means of converting changes in temperature to a numerical value. These are visible scales on older analog thermometers to digital readouts on modern ones.
The basic concept of the thermometer was known to the ancient Greeks but the thermometer as we know it gradually evolved from Galileo's 16th Century thermoscope in the 17th Century. Standardization began sometime between the 17th and 18th Centuries.
In meteorology, they are an integral part of ground-based weather stations or onboard weather balloons.
7. Hygrometer measures indicate relative humidity
Hygrometers are tools used to measure the humidity or air moisture content in the atmosphere, soil or indoors. The very first, though crude, hygrometer was invented by the Italian genius Leonarda da Vinci in around 1480.
More modern versions were created by Swiss polymath Johann Heinrich Lambert in 1755.
Older analog hygrometers come in various forms including hair tension hygrometers and sling psychrometers to name but a few. The former, as the name suggests, uses animal hair (which is hygroscopic - water-absorbing) to 'detect' changes in relative air humidity as the hair's length changes.
The latter uses a set of two thermometers, one moistened and one dry, that are spun in the air. As temperatures fluctuate above or below the freezing point of water, the 'wet' thermometer will either show a cooler temperature (if water evaporates above freezing point) or lower (if ice forms) when compared to the dry thermometer.
Modern hygrometers tend to be digital versions as they are more reliable and accurate. They use electronic sensors to detect changes in relative humidity and convert it to an easily readable numerical value.
8. Weather satellites provide a "space-eye" view
One of the newer 'kids on the block' weather satellites, is the highest tech options available to weather forecasters. They are able to view and gather large amounts of data about the Earth's weather and climate with unparalleled views.
They tend to hold either asynchronous orbits (therefore covering the entire Earth's surface) or geostationary (thereby focussing on a single spot for extended periods). As early as 1946, ambitions to put cameras into space were already being developed.
The first weather satellite, Vanguard 2, reached Earth's orbit in February 1959. This sparked the beginning of a proliferation of weather satellite launches over the next 5 decades.
From orbit, they are privy to unobstructed views of the Earth's cloud systems and are able to gather information on anything from ocean temperatures to spotting wildfires or sandstorms.
Weather satellites are unique in that they are able to offer meteorologists views of weather systems over large-scale areas offering the ability to observe weather patterns hours or days before more conventional systems like weather radar.
They are often employed to track and monitor large-scale weather patterns like hurricanes and El Nino.
9. Pyranometers measure solar irradiance
Pyranometers are a special type of weather forecast equipment used to measure solar irradiance on a given planar surface. They are also designed to detect and record solar radiation flux density (W/m2) within a wavelength range of 0.3 to 2.8 micrometers.
They have become the World Meteorological Organization's standard instrument and are covered under the International ISO 9060 standard. Such devices tend to be calibrated using the World Radiometric Reference which is maintained by the World Radiation Center in Switzerland.
Pyranometers tend to comprise of following main components:
- A thermopile, which is a sensor made of thermocouples in series and coated with a solar absorbing material.
- A glass dome to restrict the wavelengths of light able to enter the device. It also shields the thermopile from wind, rain, and convection
- An Occulting disc which measures the diffuse radiation and blocks beam radiation from the surface
These devices are normally passive and do not require any power supply at all. Modern electronic pyranometers, on the other hand, do require a small amount of electrical input.
10. Disdrometers can measure raindrops
Disdrometers are weather forecasting instruments that are used to measure the drop size distribution and velocity of raindrops (hydrometeors in the meteorological parlance).
Disdrometers come in various forms:
- Impact Disdrometers which directly measure the kinetic energy of raindrops,
- Acoustic Disdrometers that use piezoelectric sensors and diaphragms to determine raindrop kinetic energy and;
- Optical Disdrometers that use light to measure raindrops in a non-intrusive manner.
More sophisticated instruments are even able to distinguish between hailstones, raindrops, and graupel.
They tend to be used in various applications from traffic control to scientific studies to hydrology. Modern instruments employ microwave and/or laser technology as well as a 2D video that can be used to analyze snowflakes.
11. Transmissometer help determine local visibility
Transmissometers are weather forecast instruments used to measure the extinction coefficient of the atmosphere and seawater and by proxy estimate the visibility.
These instruments send narrow beams of energy, usually a laser, through the air towards a corresponding receiver a set distance away. Any photons that are absorbed or scattered by the air between the detector and sources will not reach the detector.
By determining the path transmission and extinction coefficient the local visibility can be determined.
These devices are also known as telephotometers, transmittance meters, or haze meters.
12. Ceilometer can calculate cloud height
Ceilometers are devices that use lasers or other light sources to determine the height of clouds or cloud bases, it can also be used to determine cloud thickness. They also have applications for determining aerosol concentrations and volcanic ash in the atmosphere.
They come in two general forms:
- Optical drum ceilometers use triangulation to determine cloud height from a spot of light projected onto the base of clouds. These tend to consist of a rotating projector, detector, and recorder.
- Laser ceilometers consist of a vertically aligned laser and lidar receiver within the same location. The time taken for the reflected light to return the lidar receiver enables the device to determine cloud cover height. This technology can also be prone to false positives because it can be affected by any form of particulate matter in the air (dust, rain, smoke, etc).
Ceilometers have also been shown to be fatal to birds as they get disoriented by the light beams emitted from them.
In the worst recorded ceilometer, non-laser light beam incident, approximately 50,000 birds from 53 different species died at Warner Robins Air Force Base in the United States during one night in 1954.
13. Stevenson screen's make weather forecasting more accurate
Although not technically a weather forecasting instrument, per se, the Stevenson Screen is vital nonetheless. Also known as an instrument screen, the Stevenson screen forms the basic enclosure around meteorological instruments the world over.
The main purpose of this innovation is to protect instruments from precipitation and direct heat radiation from the sun whilst allowing ambient air to circulate through to the instrumentation inside.
This is important as its absence would otherwise skew the results of any instrumentation at the weather station dependent on exposure rather than actual local weather patterns.
Stevenson screens will tend to protect instruments like thermometers, hygrometers, dewcells, barometers, and thermographs.
They were the brainchild of Thomas Stevenson who was a Scottish civil engineer who also designed lighthouses. His father was the famed Robert Louis Stevenson. Its current form is the result of some minor changes over the years with its standardization coming into effect in 1884.
Automated weather stations are progressively replacing Stevenson Screen type monitoring stations the world over.
14. Weather ships were important to shipping the world over
Weather ships aka Ocean Station Vessels were ships that were stationed strategically around the world's oceans as platforms for surface and upper atmosphere weather observations. They used to be a vital means of data collection for weather forecasting before the advent of weather satellites.
Weather ships were deployed around the Atlantic and North Pacific Oceans and reported their observations by radio. Such vessels also doubled as search and rescue ships supported transatlantic flights and helped with oceanographic research.
The concept was first proposed in 1921 by Meteo-France to support their shipping and transatlantic flight operations. These ships proved very useful during the Second World War but also suffered heavily from U-Boat attacks as they were completely defenseless.
So much so that the International Civil Aviation Organization (ICAO) established a global network of weather ships in 1948. This organization remained in place until 1985 with weather ships gradually replaced by buoys.
The last weather ship was Polarfront, known as weather station M ("Mike"), which was removed from operation on January 1, 2010. Weather observations from ships continue from a fleet of voluntary merchant vessels in routine commercial operation.
15. Buoys are very useful things
Weather buoys have largely replaced weather ships as platforms for collections weather and ocean data around the world. Moored versions have been in use since the 1950s with drifting buoys commons since the later 1970s.
A large network of buoys was established during the 1980s and 1990's around the Pacific Ocean to study El Nino systems. The first recorded weather buoy was deployed in 1927 and they became very popular during WW2.
They tend to be equipped with instruments to measure local temperature, wind speeds, and barometric pressure to name but a few.
16. Dewcells help record local vapor pressures
Dewcells are specialized hygrometers and weather forecast instruments used to determine the dew point at any one point and time. Each one consists of a small heated element surrounded by a solution of lithium chloride.
Lithium chloride tends to absorb moisture from the air which in turn increases the conduction potential across the heating element. This causes the heat to increase which evaporates moisture from the solution.
Within each dewcell resides a thermistor composite that changes the electrical resistance with changes in temperature from the heating element,
This process will continue until an equilibrium is reached, hence the dew point is ascertained. Dewcells are used for observational purposes, especially for automatic weather stations.
17. Ombrometers are pretty simple things
Ombrometers, otherwise known as rain gauges, are special devices that allow meteorologists to measure rainfall. They are pretty basic things and normally consist simply of a container (usually made of plastic) with a millimeter scale on it.
As it rains, water is collected within the tube and the amount can be readily read off the scale. More sophisticated devices have a container with a digital scale that can allow rainfall to be plotted to a computer automatically.
18. Windsocks are simple yet effective
Windsocks are another relatively simple, yet very important weather instrument. They tend to form a cone made of fabric and are designed to provide a means of indicating the direction and approximate speed of the wind.
They are used, primarily, in the aviation industry but can also be found in chemical plants. Especially where there is a high risk of gas leakage.
19. Whole or all-sky cameras are pretty cool
Whole or All-sky cameras are yet another important weather instrument. These tend to be standalone video devices that are enclosed within a weatherproof dome.
They provide a wide view of the entire sky and stream the footage to a laptop or PC over the internet. Each camera's fisheye lens provides a 180-degree view of the sky, day or night, from horizon to horizon.
They can be used to observe sunrises and sunsets, cloud activity, moving storms, starry night's sky, and much more. They tend to be used to assess cloud cover, UV index, provide timelapse photography of clouds, sky polarization, the computation of cloud base height, as well as wind speed at cloud heights.
20. Wind profilers are handy instruments
A wind profiler is another important weather instrument. These devices use radar or sound waves (SODAR) to determine wind speed and direction at various elevations above the ground.
The variables measured from wind direction and speed are useful to meteorological forecasting and timely reporting for flight planning.
21. Nephelometers (turbidimeters) are used to monitor pollution
Nephelometers are instruments used to determine the suspension of small particles within a liquid or gas colloid. They consist of a light source and a photosensor set at 90 degrees to the light beam.
Particle density is determined by the amount of light reflected from individual particles. This depends on the nature of the shape of the particle, color, and reflectivity.
A correlation is then made between the turbidity and suspended solids. These devices tend to be used to assess air quality for pollution control, climate monitoring, and visibility.
22. Ceiling balloons are another simple, yet powerful tool
Pilot balloons, or ceiling balloons, are a special kind of weather balloon that is used to measure the height of the underside of clouds from the ground. They tend to be launched during daylight hours.
Cloud heights are determined by timing the period it takes for the balloon to launch and hide within clouds. Using this information, the cloud cover height can be readily calculated.
They can also be used to acquire some other important information. For example, by tracking the trajectory, earlier with a theodolite, and today by radar or GPS, direction and speed of high-altitude winds are determined.
23. Snow gauges are also important instruments
Snow gauges, as the name suggests, are weather instruments used to calculate the amount of snowfall in a given period. They tend to consist of a vertical metric scale, for manual recordings or are equipped with ultrasonic, infrared or laser measuring systems for automated recording.
They are pretty similar in concept to rain gauges but are specially tailored to record snowfall.
24. Lightning detectors are very useful devices
Lightning detectors are a type of weather instrument used to detect lightning or light rays produced by storms. They come in three basic forms: -
1. Earth systems - These use multiple fixed antennae to detect lightning.
2. Mobile systems - These use sensitive antenna are usually carried onboard things like aircraft, and;
3. Space-based systems - These tend to consist of detectors mounted on satellites that can be used to locate lightning range, bearing and intensity via direct observation from orbit.
Earth and mobile detectors usually auto-calculate the direction and severity of lightning from a mounting location using radio techniques. Terrestrial systems can also use triangulation from multiple locations to determine the distance away from a lightning event.
25. Pan evaporators are also simple devices
Pan evaporation devices, or stilling wells, are simple weather instruments used to measure the effective evaporation at a given time. They come in several forms but "Class A" pan evaporators are the most common.
This is a cylindrical galvanized steel tank, about 1.21 meters in diameter and 25 cm deep. They tend to be mounted on a wooden platform and are kept perfectly horizontal.
Pan evaporators work by measuring the volume of water require to maintain a constant level over a set time period. This can be 6, 12, or 24 hours.
The volume of water consumed then equates to the evaporation rate, usually recorded in mm.
26. Automatic Weather Stations (AWS) are the "bees-knees"
Automatic weather stations (AWS) are the piece de resistance of weather instrumentation. These, as the name suggests, are weather stations that are completed automated.
They can be either fixed or mobile sites whose sensors relate weather data to a weather logger in the complete absence of any humans. AWS' was specially designed for use in hard to reach or remote locations (like at sea).
Automatic stations tend to come with many of the sensors listed above all connected to a central processor. The data can be stored in a logger, or transmitted by cable or radio signal to one or more remote locations.
All of the station's gubbins tend also to be contained within a waterproof housing. They are powered by a rechargeable battery, a solar panel or a wind turbine, and the number of sensors depends on the needs.
Typically an automatic station will have, as a bare minimum, a thermometer, anemometer, wind vane, hygrometer, and a barometer. They tend to be used primarily by national meteorological services but can also be employed by researchers or amateur meteorologists.