weather radar

A radar used for meteorological purposes. The term RADAR is an acronym for the English expression RAdio Detecting And Ranging (radio detection and ranging). Although it began to be expressed with its acronym in capital letters, it gradually became integrated into the language as an ordinary word (radar), in a manner similar to what is happening with DANA (dana). This instrument began to be used for military purposes during the Second World War, after having been developed in the preceding years, thanks to the contributions of scientists and engineers of different nationalities. Military aircraft began to carry installed radars that, apart from locating the positions of enemy aircraft, also detected signals coming from meteors present in the air. Once the military conflict ended, some scientists working for the US Armed Forces began to develop the possible civilian applications of those radar signals. It was from the 1970s onward that the first networks of radars, maintained by the various Meteorological Services, began to be established. Over the years, weather radars were modernized, allowing the acquisition of a three-dimensional view of the precipitating elements present in the atmosphere. Some devices also allow the deduction of the speed of movement of drops and hailstones relative to the fixed position of the radar (Doppler radar). Radar is an instrument that, through a rotating antenna, emits microwave pulses in all directions, for which it carries out a series of scans at different heights, covering 360º around itself. It works in a range of wavelengths between 1 and 30 cm. The emitted signal (a narrow beam of the aforementioned microwaves) is transmitted with a power of several megawatts, through a succession of pulses separated from each other by a few microseconds. As these beams intercept drops and hailstones on their atmospheric path, they scatter in all directions, with a fraction of them returning toward the radar, which is captured by a receiver. The time elapsed between the emission and reception of each pulse allows the distance at which the targets are located to be determined. The information obtained, coming from all the return signals intercepted by the instrument, is processed and converted into images that allow visualization of the spatial distribution - around the radar's position - of the echo-generating areas. Radar does not directly measure precipitation intensity, although those images might suggest otherwise. False echoes are often generated, which forecasters must know how to discern. Sources of error can be of the most varied kinds: from calibration failures in the device, to the presence of obstacles (despite the fact that radars are usually placed in elevated terrain locations, with a clear horizon), or also overestimations of precipitation in certain echoes. A color scale is used in radar images. Usually, blue and green are assigned to the weakest echoes (corresponding to small drops) and red and magenta to the strongest return signals (hail and large drops). Each color represents a level of reflectivity, all of them measured in decibels (dBZ).