Inside AWOS And ASOS

kmaples

Wednesday, May 19, 2021 at 02:49 PM ET

Verified

Key Takeaways:

AWOS and ASOS stations primarily differ in ownership (federal for ASOS, various for AWOS), but generally use similar sensors and are expensive to install and maintain.
While data such as temperature and wind are accurate, cloud/ceiling and visibility reports can be unreliable due to sensor limitations like a straight-up laser for clouds or short-range extrapolation for visibility.
Live radio reports from these stations update approximately once a minute, while other sources like online data or FIS-B typically update every 20 minutes.
A dollar sign ($) at the end of an AWOS/ASOS METAR report signifies that the station requires maintenance.

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How many times have you heard a report like this? “Podunk Municipal airport, automated weather observation, 2347 Zulu. Weather, wind 050 at 12 knots, gust 23 knots. Visibility 7. Sky condition, clear below 12,000 feet. Temperature 29 Celsius, dew point 17 Celsius. Altimeter 30.00 inches of mercury. Remarks, intensive glider activity 20 miles north east of the airport, use caution.”

Anyone with more than a student certificate has heard these reports countless times. And yet the AWOS and ASOS system remains a bit of a mystery to many of us. Just tune the proper frequency and don’t worry about how the data is collected or how frequently it is updated. Who owns these stations anyway? And what is the difference between an AWOS and an ASOS station? Let’s take a close look at the mysterious world of automated weather reporting.