Measuring the weather might sound like a very complicated process. But it is actually relatively simple. This is because some incredibly intelligent people have developed complex devices that can accurately measure weather.
Measuring the weather is important as it allows meteorologists to predict future weather patterns. Measuring something like wind speed is an incredibly important process as high wind speeds can be very dangerous.
But, as the wind is something we only feel and can’t see, how can it be accurately measured? What unit is wind measured in? And how on earth can we understand what the measurements mean?
How We Measure Wind Speed
Wind speed is measured using a device called an anemometer. This tricky name comes from the Greek word anemos meaning “wind”.
Meter comes from the Greek word metron meaning “to measure”. Although devices differ in style and can measure a range of different factors, the word anemometer refers to any device used to measure wind.
Anemometers were first developed around the 15th century. But the most famous style was developed in the 18th century. You have likely seen these original instruments. They look almost like a candlestick.
At the top of this base-stick are four arms with hollow hemispheres at the end. These hemispheres all face the same direction. Then, when the wind blows, it is caught within the hemispheres and the arms rotate.
But, as you can imagine, technology has come a long way since then. Modern anemometers look very different. In fact, they look like very simple devices.
As with any kind of measuring, there are several units of measurement used for wind speed. The unit of measurement recommended by the World Meteorological Organization (WMO) is meters per second (m/s).
Other units of measurement include kilometers per hour (km/h), nautical miles per hour, and knots. These are more traditional units of measurement. The WMO recommended meters per second is the most commonly used.
So, what are the most commonly used devices?
5 Most Used Devices to Measure Wind Speed
A cup anemometer is likely the kind you are most associated with (even if you don’t think you are). This is the 18th century device mentioned above.
Cup anemometers work very simply. As explained above, they are formed of a vertical stand with cups attached to the top. When the wind blows, it pushes the cups around. The faster the cups spin, the faster the speed of the wind.
Modern cup anemometers are much more technologically advanced than the original 18th century device. But the basic principle and measurement style is the same. Which is very impressive. Modern cup anemometers will usually have a digital reader attached.
Vane anemometers are very simple devices. They look similar to handheld fans. Vane anemometers can either be static or rotating and are similar in principle to cup anemometers.
They are small devices that have blades at the top which are enclosed in a circle. These blades will either be fixed or rotate. On some vane anemometers, the entire head rotates.
This is attached to the top of a digital device (called a manometer) that provides a reading. The user holds the vane anemometer by the manometer and holds it to the air. The reading appears on an LED screen.
Hot Wire Anemometer
A hot wire anemometer looks very different from the more traditional style devices. Rather than measuring the speed of the wind with rotating blades of cups, a hot wire anemometer doesn’t have any rotating features.
This style of anemometer looks very simple and is essentially a long metal rod with a handle attached. This rod is connected via a removable wire to a manometer that presents the reading on an LED screen.
To measure the speed of the wind, the hot wire anemometer (as the name suggests) heats up. When the heated wire is placed in a flowing gas stream (i.e. wind), the heat transfers from the wire to the gas. This reduces the temperature of the wire. This then changes the resistance of the wire.
It is the measurements of these differences that record the wind speed.
Pitot Tube Anemometer
A pitot tube anemometer appears to be very similar to a hot wire anemometer. It has a similar manometer which is attached by a wire to a metal rod.
The main difference, visually, is the metal rod on a pitot tube anemometer is bent at a right angle. The metal rod is also a tube, rather than a solid length of metal.
The pitot tube measures total and static pressure. This determines the velocity pressure. This results in a measurement of the wind (or air flow) speed.
Although this device can be used to measure wind, it is perhaps better suited to smaller airflows. This is still, technically, wind and they are great devices for measuring a draft.
The tube is inserted into a small space, such as an air duct, and measures the pressure. The manometer displays the measurement of velocity pressure which is then converted into velocity.
Ultrasonic anemometers work by using sound. These anemometers look more like the original cup anemometers.
But instead of cups, they feature arms that are, usually, bent at around 45 degrees. These are called transducers But these anemometers do come in a range of different sizes and styles.
An ultrasonic anemometer measures how long it takes for an ultrasonic sound pulse to travel from one transducer to the other. These are referred to as the North and South transducers.
The anemometer then compares how long it takes the ultrasonic sound pulse to travel from North to South and from South to North.
These times are then compared to how long it takes to pass between the East and West and West and East transducers. The wind speed is then determined by comparing these times as they are indicative of how strong and fast the wind is blowing.