![]() The highest officially-recognised gust at a low-level weather station was 142mph at Fraserburgh, Scotland, on 13 February 1989, but on the top of mountains, the wind is generally much stronger – gusts of 173mph were recorded on Cairngorm on 20 March 1986. ![]() However, most amateurs with weather stations cannot keep to these rules (and neither can some Met Office stations), so the general guidance is to make measurements as high as possible in an area as open as possible. In addition, because wind speed increases with height above the ground, a standard measurement height of 10 metres is adopted. The instrument response is linear and has a frequency response from 0 to 2000 Hz, sufficient to measure atmospheric turbulence directly. In that case, the anemometer will have to be well exposed, that is, kept well away from buildings or trees that can slow the wind down – “more than 300 metres away from large obstacles”, say the international rules. The corona anemometer measures the stratospheric wind and turbulence by detecting the amount of displacement the corona ion beam suffers in transversing a one inch gap exposed to the horizontal wind. Suppose wind speed at one location is to be compared with others around the country. Cup and propeller anemometers will usually indicate both values, with a choice of units – mph (miles per hour) for landlubbers or knots (nautical miles per hour – some 15% faster than mph) for sailors and airmen. Depending on the wind data’s use, the speed is either averaged over a few minutes or the maximum speed is taken - known as a gust. There are other types – ranging from a simple “ping-pong ball” anemometer you can make yourself to more accurate but more expensive sonic anemometers that rely on measuring the speed that sound travels in the wind. A cup anemometer has to be held vertically, and it will measure wind from any direction. They rotate faster in stronger winds an electronic counter converts this rotation into wind speed.Ī cheaper type is the propeller anemometer, but to get an accurate measure of speed, it has to be kept facing the wind – whose direction changes from one moment to the next, which can sometimes be tricky. The type used on weather stations and hand-held versions uses three cups on a spindle – the wind force on the open side of the cup is greater than that on the rounded side, making the cups rotate. But how do we measure its speed?Ī device for measuring wind speed is known as an anemometer, and there are many different types. As well as meteorologists, many other people are interested in how fast the wind is blowing, ranging from athletes such as parachutists and sailors to those concerned with hazardous winds, such as air traffic controllers and crane operators. Wind is simply the movement of air, but sometimes this movement can be pretty fast! Those of us in the South of England have recent memories of the St Jude’s Day storm on 28 October 2013 and the disruption caused by gusts of up to 99mph.
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