Detection of in-flight icing conditions through the analysis of hydrometeors with a vertically pointing radar

According to the Air Line Pilots Association, 97% of icing accidents take place during the approach, landing, holding, or go-around phase of flight. For this reason, identifying hydrometeors, especially the supercooled liquid water (SLW) that causes icing, in a vertical column above the airport is a crucial step in reducing the number of icing accidents. Armed with information about the type and location of any precipitation, pilots, meteorologists, and air traffic controllers can safely route airplanes away from danger. In this study, we aim to provide a now-cast of icing condition in the vicinity of an airport using a Vertically Pointing Radar (VPR).

The VPR is an X-band Doppler radar, developed at McGill University, which measures reflectivity, Doppler velocity, and the distribution of hydrometeor fall speeds. With these variables, collected at 10-minute averages in the horizontal and 75m resolution in the vertical, a computer can be programmed to identify the melting layer, types of precipitation, and location of precipitation. Further analysis of the data provides information about potentially dangerous icing regions. From the distribution of fall speeds, one can separate out modes, or peaks in the power returned, and the existence of more than one mode is a good indication of a hidden type of hydrometeors, such as SLW. In addition, a relationship between reflectivity and Doppler velocity provides information on the type of hydrometeor and warns of conditions like riming, an excellent indication that there is SLW in the region.

When combined into one system and run continuously over time, the 5 algorithms in this study will be able to provide a timely, affordable, and valuable warming as to the level and extent of icing conditions occurring in the airport region. When considering the value of the information provided by the VPR, it is important to note that it costs only a tiny fraction of typical scanning radar.