Mesaba Airlines supplemental PIREP program

Voice pilot reports (PIREPs) are a very important data source used in meteorological research. PIREPs are used in forecasting tools to help to predict the occurrence of meteorological phenomena, like icing or turbulence. PIREPs are also a tool used to verify the output of these forecasting tools. Pilots are encouraged to provide voice PIREPs throughout the course of their flights. While these PIREPs document the cases in which weather events occur, documented null PIREPs are relatively infrequent. In the effort to gather more thorough data, Mesaba Airlines, an affiliate of Northwest Airlink, has agreed to provide supplemental hand-written PIREPs as part of the Great Lakes Fleet Experiment. The pilot documents the conditions at take off, in-flight, and landing, even if there are no weather events to report. Between January and June of 2005, Mesaba Airlines has sent more than 3,500 special PIREPs, with over 2,000 documented cases of either no icing or no turbulence. In addition to direct use of these reports for evaluation of icing/turbulence forecasts, these special reports will be compared to coincident automated TAMDAR observations.

Before the data can be analyzed or used, it is necessary to apply quality control procedures to verify that the data received are conceivable and reasonable. Temperatures and flight levels outside the respective range are flagged as questionable data and removed from any further analysis. The data are then broken down and compared to investigate possible relations between severity of icing and turbulence, flight level, temperature, and precipitation. As a verification process, an attempt is made to match the hand-written PIREPs to the actual voice PIREPs. For this evaluation, a cylinder of airspace and time is defined in which all nearby voice PIREPs are matched and compared with the special hand written PIREPs (Wolff, 2003). Because most of the voice PIREPs are only recorded when events of icing or turbulence occur, we restrict this comparison to light or greater icing/turbulence severity. We expect to find that if there are other aircraft in the area at the given time, the hand-written PIREPs will match up well with the voice recorded PIREPs.