Weather radar uses microwaves to detect approaching storms and severe weather. Microwaves travel between 300 GHz and 300 MHz frequencies. Antennas collect and relay radar pulses back to the station
Intermediate frequency is a carrier wave shifted between transmission and reception steps. Invented by Major Edwin Armstrong in 1918 during World War I. Initially used for military signals, later adopted by radar development
WWII radar operators discovered weather echoes masking enemy targets. David Atlas developed first operational weather radars in US. J.S. Marshall and R.H. Douglas formed Stormy Weather Group in Canada. First radar observation of tornadic thunderstorm hook echo in 1953
The Doppler effect describes the frequency change in waves due to observer motion. Christian Doppler first proposed it in 1842, confirmed by Buys Ballot in 1845. The effect occurs when the source moves towards or away from the observer
STAP is a radar signal processing technique for target detection. Developed by Brennan and Reed in 1970s, formalized in 1973. Uses two-dimensional filtering with multiple spatial channels. Applies adaptive weights based on interference environment statistics
Altimeter measures altitude above fixed level using atmospheric pressure. Most aircraft use pressure altimeters with nonlinear calibration. Skydivers and hikers use wrist-mounted versions