Definition
A long-range Air Route Surveillance Radar (ARSR) that has been digitally processed to filter out most weather returns, leaving a cleaner display of aircraft targets. Because precipitation echoes are largely removed, narrowband ARSR provides only limited weather information to the controller — typically shown as one or two basic intensity levels rather than the detailed weather depiction available on broadband or terminal weather radar.
Plain English
It is the en route radar used by air traffic controllers, but with most of the weather echoes filtered out so aircraft show up clearly. The trade-off is that controllers using it can only see very basic weather information, not detailed storm intensity.
Context Anchor
Seen in instrument flying discussions about what ATC radar weather displays can and cannot show to controllers.
Derivation
‘Narrowband’ refers to the narrow range of signal information passed through after digital processing — most of the raw radar return, including weather, is stripped away, leaving a thin slice of data focused on aircraft targets. Contrast with ‘broadband,’ which carries the full radar picture including weather.
Why Pilots Care
Enables controllers to give timely weather advisories and route aircraft safely around precipitation.
Grounding Statement
If the source is narrowband ARSR, think “rough weather outline,” not “detailed storm map.”
Intuition Check
Narrowband does not mean the radar beam itself is narrow. Here it means the radar information being sent or displayed is limited in detail.
Example Sentence 1
Because Center was working narrowband ARSR, the controller could only report light or heavy precipitation along our route, not detailed cell locations.
Example Sentence 2
Narrowband ARSR coverage extends hundreds of miles, giving enroute controllers a broad view of both traffic and weather.