What source provides real-time information about the presence of icing?

The source that provides real-time information about the presence of icing is the PIREP, or Pilot Report. PIREPs are reports made by pilots in flight that describe conditions encountered during their journey, including important weather phenomena such as turbulence, cloud cover, and icing. These reports are valuable because they reflect actual conditions experienced by pilots and can provide updated information to air traffic controllers and other pilots about the current state of the atmosphere.

In contrast, NOTAMs (Notices to Airmen) offer information on temporary flight restrictions, hazards, and other operational information but do not provide real-time weather conditions. Weather stations provide broader meteorological data but may not give specific information regarding the presence of icing at a particular location. AWOS (Automated Weather Observing System) also reports on a variety of weather conditions, but unlike PIREPs, it does not capture the direct experiences of pilots regarding icing. Thus, PIREPs are the most reliable source for real-time icing information encountered in flight.