Radars in meteorology

Radar (acronym for radio detection and ranging) monitoring techniques  are used to record the position of objects of any size, from ships or planes to particles and molecules.
The techniques were born during World War II for military purposes.
In meteorology, with the radar system it is possible to identify and follow perturbation systems, using the reflection of the radio waves on the drops of water and ice crystals in the clouds
The state of the art radars exploit the Doppler effect. This effect  makes the length of an electromagnetic signal vary, depending on the movement of the object that issues it. With the Doppler effect the whistle of a train  will sound more acute  in our ears as the train draws near, and the frequency will be lower as the train moves away, even though the frequency of the train’s signal is always the same.
A Doppler radar not only identifies an object, but it can also assess its distance, speed and direction of movement, and it can measure the relative density of the objects that are observed. This monitoring system has made available to the meteorologists an enormous quantity of new and interesting data, and it is possible to obtain data on the speed and direction of storm systems,  thus enabling increasingly precise and detailed forecasts. In particular, this system is utilized to follow the movement and evolution of tropical storms, hurricanes and tornadoes in real time. At present, the Doppler radar network on ground is still incomplete, however in a few years it should cover the Earth’s surface completely.

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