The Automated Surface Observing System (ASOS) is a surface weather observing system being implemented by the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the Department of Defense (DoD). ASOS is designed to support aviation operations and weather forecasting.
This guide is designed to provide basic ASOS information to pilots and other aviation users. Refer to the ASOS Quick Reference Handbook published by the National Weather Service for additional information.
If your a pilot you probably have this information, but if not, here it is.
If your not a pilot, but have interest in weather then the ASOS system might be interesting to you also. I am not a pilot, but I have worked a few dozen aircraft crashes, and am interested in anything that prevents planes from crashing.
The ASOS will provide minute-by-minute observations and perform the basic observing functions necessary to generate a surface weather observation and other aviation weather information. Pilots need to understand tha t automated and manual weather observations are different and have different operational implications.
ASOS and the human observer differ in methods of data collection and interpretation. For elements such as pressure, air temperature, dew-point temperature, wind, and precipitation accumulation, both the automated system and the observer use a fixed location and time-averaging technique.
For visual elements (i.e., sky condition, visibility, and present weather), observers use a fixed time, spatial-averaging technique while the ASOS uses a fixed location, time-averaging technique. Although this is a fundamental change, the manual and automated techniques yield similar results within the limits of their respective capabilities.
Please refer to the FAA’s Aeronautical Information Manual for operational guidance and to the FAA’s Airport/Facility Directory, aeronautical charts and related publications, for ASOS broadcast frequency, dial-in telephone number, and location information.