The Automated Surface Observing System (ASOS) and the older Automated Weather Observing System (AWOS) are sensors used to measure and record hourly and significant weather conditions at airports across the United States. The newer Automated Weather Sensor System (AWSS) is the successor to AWOS, reporting once per minute. They are implemented cooperatively, with the National Weather Service operating ASOS and AWOS and the Federal Aviation Administration (FAA) distributing information to pilots. This is usually via an automated VHF airband radio frequency (118~136MHz) at each airport, broadcasting ASOS or AWOS weather information, often via the Automatic Terminal Information Service (ATIS).
ASOS, AWOS, and AWSS units record temperature, visibility (haze or fog), precipitation types and amounts, wind direction and speed, humidity and dewpoint, barometric pressure and altimeter, sky cover and ceiling, and thunder. Freezing rain is recorded with a vibrating wire, which stops vibrating as ice accumulates. Regular reports are made hourly, often a few minutes before the hour. Significant changes in weather during the hour are also normally reported, such as rain changing to snow, approaching thunder, or heavy rain. Some stations at smaller airports do not report overnight.
The data helps meteorologists, pilots and flight dispatchers prepare and monitor weather forecasts, flight routes, and provide necessary information for safe takeoffs and landings. AWOSs are categorized as either "federal" or "non-federal". Federal AWOSs were purchased and are currently maintained by the FAA. Non-federal AWOSs are purchased and maintainted by state government, local government, and private organizations. The AWOS does not predict weather, but sends current information to weather offices where forecasts are produced using this information along with computer model outputs, weather satellite photos, and weather radar images, to name a few.
Every hour, on or just before the hour, the data is made available to off-site users by those AWOSs on Service A (long-line telephone communication) or communications satellite uplink. The aviation community, which is one of the largest users of environmental data , is the major user of the AWOS information. AWOS is also available by dial-up telephone at each location.
Not all U.S. government weather stations are NWS- or FAA-run. The Remote Automated Weather Station (RAWS) system is run by the U.S. Forest Service and Bureau of Land Management and monitored by the National Interagency Fire Center , mainly to observe potential wildfire conditions.
External links