Definition
A network of automated weather stations, typically located at airports, that continuously measure and report surface weather conditions including wind, visibility, cloud height, temperature, dew point, altimeter setting, and precipitation. ASOS broadcasts this information by radio on a discrete frequency and by telephone, updating once per minute and issuing special reports when conditions change significantly.
Plain English
An automatic weather station at an airport that takes regular measurements of the local weather and broadcasts them so pilots can listen in before takeoff or landing.
Context Anchor
Pilots encounter ASOS during preflight planning, before takeoff, while approaching an airport, or any time they need current airport weather information.
Why Pilots Care
Supplies real-time weather data pilots use for takeoff, landing, and flight planning decisions at airports without continuous human observers.
Intuition Check
Do not assume “automated” means perfect or complete. ASOS reports what its sensors measure at that location; nearby weather can still be different.
Example Sentence 1
Before departing, the student tuned the ASOS frequency and copied down the wind, visibility, and altimeter setting.
Example Sentence 2
ASOS readings showed gusty winds that prompted the pilot to choose a different runway.