iU 5~ 3 
 
 Automated Surface 
 Observing System (Asusj 
 
 New Automated Surface Observing 
 Systems (ASOS) are currently being 
 installed at over 850 locations throughout 
 the U.S. The ASOS program is a joint effort 
 of the National Weather Service (NWS), 
 the Federal Aviation Administration (FAA), 
 and the Department of Defense (DOD). 
 When installation is completed in the mid- 
 1990s, the ASOS systems will serve as the 
 nation's primary surface weather 
 observing network. ASOS is designed to 
 support weather forecast activities and 
 aviation operations and, at the same time, 
 support the needs of the meteorological, 
 hydrological, and climatological research 
 communities. 
 
 With the largest and most modern 
 complement of weather sensors, ASOS 
 will significantly expand the information 
 available to forecasters and the aviation 
 community. The ASOS network will more 
 than double the number of full-time surface 
 weather observing locations. ASOS works 
 non-stop, updating observations every 
 minute, 24 hours a day, every day of the 
 year. 
 
 Getting more information on the 
 atmosphere, more frequently and from 
 more locations, is the key to improving 
 forecasts and warnings. Thus, ASOS 
 information will help the NWS to increase 
 the accuracy and timeliness of its forecasts 
 and warnings — the overriding goal of the 
 NWS modernization. 
 
 The primary concern of the aviation 
 community is safety, and weather 
 conditions often threaten that safety. A 
 basic strength of ASOS is that critical 
 aviation weather parameters are 
 measured where they are needed most: 
 airport runway touchdown zone(s). 
 
 ASOS detects significant changes, 
 disseminating hourly and special 
 observations via the NWS and FAA 
 communications networks. Additionally, 
 ASOS will routinely and automatically 
 provide computer-generated voice 
 observations directly to aircraft in the vicinity 
 of airports, using FAA ground-to-air radio. 
 These messages will also be available via 
 a telephone dial-in port at the ASOS. 
 
The ASOS sensors include: ftEfcffttSYL IMm 
 
 u ^versSty TA7E 
 
 • Cloud Height • Visibility • Precipitation Identification 
 
 • Freezing Rain • Pressure • Temperature/Dew Point JUL xQ ]ggo 
 Wind Direction and Speed • Precipitation Accumulation DOCUMENT^ 
 
 A0Q0DElE3MEflt> 
 
 ASOS Features 
 
 Observes, formats, archives and transmits ob- 
 servations automatically. When preselected 
 weather element thresholds are exceeded 
 (e.g., the visibility decreases to less than 3 
 miles), a "special" report is transmitted. 
 
 Reports basic weather elements: 
 
 • Sky condition: cloud height and amount (clear, 
 scattered, broken, overcast) up to 12,000 feet 
 
 • Visibility (to at least 10 statute miles) 
 
 • Basic present weather information: type and 
 intensity for rain, snow, and freezing rain 
 
 • Obstructions to vision: fog, haze 
 
 Pressure: sea-level pressure, altimeter setting 
 
 Ambient temperature, dew point temperature 
 
 Wind: direction, speed and character (gusts, 
 squalls) 
 
 Precipitation accumulation 
 
 Selected significant remarks including - 
 variable cloud height, variable 
 visibility, precipitation beginning/ ^ 
 ending times, rapid pressure £• 
 
 changes, pressure change ten- 
 dency, wind shift, peak wind.