Rain radar

"Weather radars send out electromagnetic pulses to measure the location and intensity of precipitation - including rain, hail and snow - in real time. Radar works by sending out electromagnetic pulses and measuring how long they take to return from a target, e.g. an aircraft or a ship. It has been known for many years that other objects can also create a return, e.g. flocks of birds or precipitation. It was soon decided that being able to 'see' precipitation would be of great value, so much investigation was done to perfect this method. In simple terms, a weather radar sends out a pulse at a wavelength of 5.6 cm which is reflected by precipitation (this is then compared to a number of rain gauges and adjusted accordingly). In operational use, weather radar is in fact the only means available for measuring the location and intensity of precipitation in real time." (Met Office n.d.)
 

Sources

Met Office. n.d. “Rainfall Radar.” Accessed April 16, 2021. https://www.metoffice.gov.uk/weather/learn-about/how-forecasts-are-made….