Major Systems Overview

Information from Sensor Networks


Surface Observations

Public Sector Network

• ASOS deployed in early to mid-1990s by NWS and FAA

• Replaced human observer in most locations

• Located at airports, WSFOs, etc.

• 813 FAA and NWS ASOS

• 180 DOD ASOS sensors

• 1300 Federal AWOS

• ~500 Non-federal AWOS

• Another ~8500 COOP sensors

Private Sector Networks

• Deployed over last 20 years

• School networks, local and state municipalities, utilities, television stations, private met companies

• In most cases, provider maintains ownership rights to data

• Approximately 10,000 sensors deployed

• Also, ~2500 road-weather sensors deployed

Other Federal Government Networks

• Deployed in last 20 years


• ~13,000 sensors


• ASOS contains a hygrothermometer, mid-1990s by NWS and FAA cloud height indicator, and precipitation identifier

• Some sites have icing detectors used for reporting freezing rain

• Thunderstorm information is also available at most sites


• Provides dewpoint, temperature, present weather, and visibility

• Measures continuously and updates data every minute, but does not transmit them

• Transmits an observation when SPECI criteria are met

• All observed data are used in the algorithms to create the final observation. The algorithms are complex and vary from sensor to sensor


• Transmits an observation every 20 minutes


• All of the ASOS sensors are on a 90-day preventive maintenance schedule

• The ASOS Operations and Monitoring Center monitors the ASOS 24/7 and opens trouble tickets for flagged or missing data

• ASOS sensor outages vary from 24 to 120 hours depending on the type of outage and the level of activity of the airport

• Human observers augment the observations at all federal towered airports while tower is open

• At larger airports, dedicated weather observers are on duty 24 hours a day to augment and backup the ASOS

• NCDC can acquire data from nearby cooperative observing stations to replace missing data

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