“Severe Icing: Urgent PIREP!” Severe Icing Across the United States from 2002-2010: Relationship to icing type, terrain, altitude, aircraft type, and climate

The bane of all pilots – severe icing! Whether clear, rime or mixed, any ice in the category of severe must be avoided by pilots. This study analyzed all of the severe icing pilot reports across the United States from 2002 through 2010. This encompasses the entire pilot report on-line database (except for a few months in 2001) from the National Climatic Data Center (NCDC). Only “severe icing” reports were studied, i.e., not moderate to severe, not moderate, not light, etc. Of these reports, they were categorized in terms of ice type, urgent, flight altitude, aircraft type, time of year, El Nino or La Nina or neither year, Southern Oscillation Index (SOI), terrain, region of the U.S. and so on.

It comes as no surprise that the majority of the “severe only” pilot reports were “urgent” PIREPs. Of these severe icing PIREPs, the months with the most reports of severe icing were, in order: January, December, March, April, February, November, October/May (tied), and then a huge drop to September, June/July (tied) and August. The number of severe icing PIREPs decreased by almost 90% over the decade. The possible reasons behind this fact will be discussed. The ice type is mostly rime, followed by mixed and then clear. The altitudes are divided by seasons and there are very interesting climate effects observed in the data.

All of the results along with conclusions regarding aircraft type, flight altitude, region of the United States and climate will be discussed.