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How does a weather radar work?


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Swiss federal authoritiesSwiss federal authorities

The complex components of a weather radar generate an electromagnetic signal and emit it through the antenna into the surrounding atmosphere. The signal interacts with rain, snow or hail, causing backscattering towards the antenna. The antenna captures this very weak backscattering signal and sends it to the digital electronic system for later processing. Echo intensity enables to determine the type of precipitation involved, while the signal’s transmission is used to calculate the distance between the weather radar station and the precipitation itself.

The weather radar antenna has a diameter of 4.2m and rotates continuously on its axis - 24 hours a day, 365 days a year. Its elevation changes at each turn, so that the antenna can scan a cylindrical volume of atmosphere up to 240 km wide and 18 km high. It takes 5 minutes to complete a scan of this volume. After 20 rotations at different elevations, the antenna returns to its initial position and a new cycle begins.

The signal back-scattered towards the antenna is captured, amplified and processed for easier interpre-tation of the scores of signals recorded by the weather radar. Particular care must be put in eliminat-ing the largest possible amount of disturbance, such as echoes caused by nearby mountains.

The signals received by the weather radars of the MeteoSwiss network are sent to a data processing centre to generate a map of precipitation areas in Switzerland and in the neighbouring regions.

A specific colour code is used to identify precipitation areas of higher or lower intensity. MeteoSwiss updates this map every 2,5 minutes, thus allowing for real-time monitoring of movements and development of precipitation areas.

This video is available only in Italian.

Che cosa si intende con il termine "Radarmeteorologia"? Questo filmato sulla radarmeteorologia è stato prodotto e divulgato in occasione dell’ottantesimo anniversario del centro regionale di MeteoSvizzera a Locarno-Monti.