Weather radar

Weather radar detects precipitation by transmitting radio waves and measuring energy reflected back by raindrops, snowflakes, hail, or other targets. Changes in the returned signal reveal precipitation’s location, intensity, and motion.

Radar equation: An equation relating transmitted power, target properties, distance, and received power in a radar system. It explains why echoes weaken with distance and how returned power relates to precipitation.
Electromagnetic radiation: Energy that propagates through space as coupled electric and magnetic fields. Radio waves are the part of the electromagnetic spectrum used for radar sensing.
Weather surveillance radar: A radar system designed to monitor precipitation and storm structure over a broad area. It is the operational form used for routine regional weather monitoring.
Weather satellite: A satellite that observes atmospheric conditions and weather from orbit. Satellites observe broad cloud patterns, while radar measures precipitation within its coverage.
Radar bright band: A layer of enhanced radar reflectivity near the melting level of falling snow. Melting snow can make radar overestimate precipitation compared with rainfall at the ground.
Radar reflectivity: A measure of the strength of radar echoes from targets within a sampled volume. Reflectivity is the principal quantity used to estimate precipitation intensity.
Mie scattering: The scattering of electromagnetic waves by particles whose size is comparable to the wavelength. Many raindrops scatter weather-radar wavelengths in this regime.
NEXRAD: The United States network of operational Doppler weather radars, also called WSR-88D. Its nationwide observations support forecasts and severe-weather warnings.
Weather radar network: A group of weather radars whose observations collectively cover a larger region. Overlapping stations address the limited range and blind areas of individual radars.
Anomalous propagation: The bending of radar beams under unusual atmospheric refractive conditions, producing unexpected echoes. Beam bending can create ground echoes that resemble precipitation.

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