AWOS – Automated Weather Observing System
In the US there are federally owned/operated AWOS and non-Federal AWOS that are commercially manufactured. AWOS generates and transmits minute by minute updates of the weather at the airport and reports on a variety of meteorological factors, depending upon the system making the data virtually real-time. AWOS have nine levels of reporting, but most airports will have some variety of AWOS-III. While AWOS reports are automated, they may include human observations when visibilities are reduced, if the AWOS is unmonitored, an “AUTO” tag is included in the textual output.
ASOS – Automated Surface Observing System
ASOS systems are mostly operated and controlled by the NWS, DOD and, occasionally, the FAA. They have a level of reporting comparable to an AWOS-III up to IV Z and offer hourly reports on barometric pressure, wind speed and direction, DA, visibility, sky condition, ceiling height, precipitation, and in some cases thunderstorm and freezing rain detection.
ASOS systems are the National Weather Service’s primary climatology network for observing and reporting weather in the United States and may be found in locations other than airports if they serve to improve weather awareness in locations pertinent to the public.
ATIS – Automated Terminal Information Service
An ATIS system provides pilots with essential airport information beyond just weather data. The supplemental information is provided by a human monitoring the system from the tower. You will only see an ATIS system at a towered airport. When the tower shuts down, the ATIS system typically reverts to an ASOS or AWOS system. ATIS reports are published hourly at 55 minutes past the hour, unless the weather is rapidly changing and additional information is deemed necessary. In addition to weather data, the ATIS often provides information about the active runway, runway surface conditions, and other pertinent information such as notices about construction.