Definition
A measure of how strongly a target — typically precipitation particles — returns radar energy back to the radar antenna. In weather radar, reflectivity depends mainly on the size, number, type, and phase (liquid or ice) of the precipitation particles within a given volume of the atmosphere. Higher reflectivity values indicate larger or more numerous precipitation particles and are commonly displayed as more intense colors on a radar image.
Plain English
How strongly rain, hail, or snow bounces the radar signal back. Bigger drops and more of them bounce more energy back, which shows up as brighter or more intense colors on the radar picture.
Context Anchor
Seen in thunderstorm and weather radar discussions, especially when interpreting radar colors, storm cells, and areas of heavy precipitation.
Derivation
From radar (Radio Detection And Ranging) plus reflectivity (the quality of reflecting). Reflectivity comes from the Latin reflectere, meaning to bend back. So radar reflectivity is literally how much radar energy is bent back toward the source — a useful anchor because the radar is measuring the echo it gets back from precipitation.
Why Pilots Care
Higher reflectivity values signal more intense precipitation and greater risk of hail, severe turbulence, and wind shear that can threaten aircraft structural integrity and control.
Analogy
It is like shining a flashlight into falling rain at night. Heavier rain sends more light back to your eyes, but the brightness alone does not tell you everything about the wind or danger around it.
Grounding Statement
On a radar picture, radar reflectivity is the reason one part of a storm may appear weak while another part shows a strong, intense return.
Intuition Check
Do not read radar reflectivity as a direct danger meter. It means “how strong the radar return is,” not “exactly how severe the storm is.”
Example Sentence 1
The pilot saw a core of high radar reflectivity along the route and deviated 20 miles south to stay clear of the thunderstorm.
Example Sentence 2
Reflectivity returns above 45 dBZ prompted the crew to request a different routing from ATC.