Definition
False or misleading returns shown on a NEXRAD weather radar display that do not represent actual precipitation. These returns can be caused by ground clutter, anomalous propagation of the radar beam, interference, biological targets such as birds or insects, or processing artifacts in the radar system.
Plain English
Stuff that shows up on a weather radar picture but isn't really weather. The radar is reporting something that isn't there, or is misreading what is.
Context Anchor
Seen when interpreting NEXRAD weather images during preflight planning or on a cockpit weather display, especially when a colored area does not match other weather information or what the pilot can see.
Derivation
Spurious comes from the Latin spurius, meaning 'false' or 'illegitimate.' In aviation use, spurious data means data that looks real but isn't — readings the radar produced that don't reflect real weather.
Why Pilots Care
Acting on spurious returns can trigger unneeded course changes or cause pilots to dismiss actual hazards.
Analogy
It is like a smudge on a windshield that looks like something outside. The mark is real on the glass, but it does not mean there is an object in the sky at that spot.
Grounding Statement
If the radar display shows weather that is not actually present in that place, the display is showing spurious radar data.
Intuition Check
Do not assume every colored radar return is real weather. Spurious means the display is showing false or misleading information, not confirmed precipitation.
Example Sentence 1
The instructor pointed out a band of green returns near the radar site and explained it was spurious radar data caused by ground clutter, not light rain.
Example Sentence 2
Before deviating around a cell, the crew verified that the return was not spurious radar data by cross-referencing a second weather source.