A Comparison of Icing Pilot Reports to Weather Conditions

National Center for Atmospheric Research, Boulder, CO Pilot reports, which are referred to as PIREPs, are radioed in during flight to help expand the view of the current flight, current weather, and current icing conditions. PIREPs may contain the location from where the plane took off, the approximate location of the plane at the time of the report, the time of the report, the flight altitude, the aircraft type, cloud tops, air temperature, and the type and severity of icing and turbulence. When all of the information is received, it is then encoded and sent to the weather offices and air traffic control stations. PIREPS are very helpful in the analysis of the current weather, icing, and turbulence conditions over particular areas, but they alone cannot be used as a tool to predict the type of weather and the presence of icing, let alone the severity and type of icing that could occur. The Current Icing Product (CIP) does this by blending data from geostationary satellites, national radar, the lightning detection network, surface reports of cloud cover, ceiling heights, and precipitation types, and PIREPs with output from a numerical weather prediction model. Icing PIREPs from January, April, July, and October 2008 will be compared to weather scenarios identified by the CIP in order to determine which weather scenarios produce the most icing PIREPs, how the distribution of icing scenarios changes by season, and what icing severities are most common for each scenario and season. This will help to give a better understanding of the correlation between the type of weather and the frequency and severity of icing by season.