And Now, the Weather... by Alison Maloney

Author:Alison Maloney
Language: eng
Format: epub
Publisher: Ebury Publishing

Weather Balloons and Radiosondes

A radiosonde is a small battery-powered device that is sent up into the air by a helium-filled balloon, or weather balloon, on a daily basis. It typically ascends at a rate of 5 metres per second and, as it does, it sends data on temperature, humidity and wind to a receiver every two seconds. On average it will reach a height of 25 km before the drop in pressure causes the balloon to burst and the radiosonde to drop to the ground with the aid of a small parachute, with a GPS tracking its whereabouts.

The first radiosonde was launched in January 1929 in France by Robert Bureau, who also named the device. A year later a more practical version, developed independently by Russian Pavel Molchanov, was launched and quickly became the standard because it converted its readings into Morse code, making it more user-friendly.

In Finland, Professor Vilho Vaisala was busy designing his own version and, after first flying it in 1931, he established a company to make and market his device in 1936. Today, the Vaisala company is the largest producer of radiosondes in the world, and the Met Office currently uses the Vaisala RS92 radiosondes, as do many meteorological services around the world, including the US National Weather Service.

The Met Office now has six operational launching sites in the UK of which two – Lerwick in Shetland and Camborne in Cornwall – are manned. The other four, which are automatic, are in Castor Bay (Northern Ireland), Watnall (Nottingham), Herstmonceux (south of London) and Albemarle (near Newcastle).

Although radiosondes and weather balloons provide accurate readings, their landings are not always so accurate. They have been known to get caught in power lines, crack the occasional windscreen and even break panes of glass in conservatories. The Met Office do pay for any damages which occur and say the incidents are few and far between, with someone putting in a claim about every six months. Not bad considering they launch 3,500 balloons a year.

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