Definition
A logarithmic unit used on weather radar to express the strength of the signal reflected back from precipitation. Higher dBZ values indicate larger or more numerous precipitation particles in the radar beam, which generally corresponds to heavier rainfall or more intense storm activity. ATC radar weather displays use dBZ values to assign precipitation intensity levels (light, moderate, heavy, extreme).
Plain English
A number that tells the radar operator how strongly precipitation is bouncing the radar signal back. Bigger numbers mean heavier or more intense weather.
Context Anchor
Seen on ATC radar weather displays and weather radar products that show precipitation intensity near the flight path.
Derivation
The 'dB' is decibel, a logarithmic ratio used in many fields to compare signal strengths. The 'Z' refers to reflectivity factor, the radar variable that measures how much energy precipitation reflects back. Putting them together: dBZ is the reflectivity expressed on a decibel scale, which keeps the numbers manageable across a huge range of precipitation strengths.
Why Pilots Care
Higher dBZ values help identify areas of heavy precipitation and potential thunderstorms so pilots can plan safe routes around them.
Analogy
Like the decibel scale for sound, dBZ is not a simple ruler. A small increase in dBZ can mean a much stronger radar return.
Grounding Statement
A light drizzle might show around 20 dBZ, a steady rain around 30 dBZ, and a strong thunderstorm core 50 dBZ or higher.
Intuition Check
Do not read dBZ as a direct danger score or as a straight-line scale. It shows the strength of the radar return; pilots still use the full weather picture to decide how to avoid the area.
Example Sentence 1
The controller advised that a cell of 50 dBZ returns lay along the route, and offered a deviation twenty miles south.
Example Sentence 2
Areas showing 35 dBZ or higher on the radar display usually indicate moderate rain that may require closer monitoring.