Definition
A logarithmic unit used by weather radar to express how strongly precipitation reflects the radar's signal back to the antenna. Higher dBZ values indicate larger or more numerous precipitation particles within the radar beam, and therefore more intense precipitation. Values are colour-coded on radar displays, with low dBZ values shown as light returns (drizzle, light rain) and high dBZ values shown as heavy returns (heavy rain, hail, intense thunderstorm cores).
Plain English
It's the number weather radar uses to show how heavy the rain or storm is. Bigger number means heavier precipitation and a stronger storm.
Context Anchor
Seen in ATC radar weather displays and weather avoidance discussions when controllers describe or display areas of precipitation intensity.
Derivation
dB' is the decibel, a logarithmic unit comparing one value to a reference. 'Z' is the symbol for the radar reflectivity factor, which relates to the size and number of precipitation drops in the beam. So dBZ literally means 'reflectivity expressed in decibels.' The logarithmic scale is used because reflectivity values vary across an enormous range, and decibels keep the numbers manageable.
Why Pilots Care
Helps pilots judge the intensity of storms ahead so they can request vectors or deviations to avoid hazardous weather.
Analogy
Think of dBZ like a volume reading for weather on radar. A low number is a quiet return; a high number is a loud return. It does not tell you everything about the storm, but it tells you how strongly the radar is seeing it.
Grounding Statement
If the radar beam hits light rain, the return may be weak; if it hits heavy rain or hail, the return is much stronger and the dBZ value rises.
Intuition Check
dBZ is not a direct measurement of turbulence, cloud height, or storm danger. It measures radar return strength, which often points to more intense precipitation.
Example Sentence 1
ATC reported a line of weather ahead with returns of 45 to 50 dBZ, so we requested a 20-degree deviation to the south.
Example Sentence 2
Onboard radar showed isolated cells below 35 dBZ, so we continued without rerouting.