The development of radar for meteorology

Nowadays, radar (RAdio Detection And Ranging) images are routinely shown to users of weather data and are even displayed on TV for viewers. The ability to forecast river levels and flooding risk has been taken to new levels of sophistication.

Current status of Met Office radars

• Fifteen Met Office radars operating in the UK
• Each radar has a range of 255 km
• Each radar completes a series of scans about the vertical axis at each of four elevation angles every five minutes.
• Radar data are sent to the Met Office every 15 minutes where further processing takes place to produce a composite picture of the precipitation.
• Rainfall radars show rain, hail and snow, but drizzle often cannot be detected because the drizzle droplets are usually too small to be ‘seen’.
• These data are vital components of a successful forecast and crucial for issuing warnings of heavy rainfall events.

History of radar

1864	British physicist James Clerk Maxwell develops equations governing the behaviour of electromagnetic waves, including the laws of radio-wave reflection.
1887	German physicist Heinrich Hertz shows that radio waves can be transmitted through different materials, and finds a way to measure their speed.
1901	Guglielmo Marconi transmits radio waves across the North Atlantic.
1924	Sir Edward Appleton measures the height of the ionosphere with radio echoes.
1934	A ‘death ray’ to disable machines and people is suggested, but destruction at a distance is not thought possible. However, energy reflected by objects such as aircraft should be detectable at useful ranges.
1935	Sir Robert Watson-Watt develops the UK’s first practical radar system.
1939	The UK has a chain of radar stations located along the south and east coasts to detect attack from both air and sea.
1940s	Wartime radar operators find additional echoes appearing on their displays. These are found to be from precipitation such as rain or snow — physicists had not appreciated the sensitivity of radar.
1960s	Further development of radar for weather applications is slow, but in the late 1960s the Met Office collaborates with the Royal Signals and Radar Establishment to use radar for measuring precipitation, and to generate imagery from the data.
1970s	A national weather radar network is planned, in co-operation with the water industry, with the first two installations located in the north-west of the UK and in the London area. This enabled forecasters and other users of weather radar to fundamentally reassess precipitation patterns and spawned some new ideas and theories in weather forecasting.
1980–90s	The use of radar images becomes more extensive allowing users (e.g. the military, Environment Agency) to adapt behaviour, procedures, etc. in line with the weather.

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