The 2013 Buffalo Area Icing and Radar Study (BAIRS)
March 6, 2015
The Next Generation Weather Radar (NEXRAD) network completed a dual polarization upgrade in 2013. The radars now can be used to sense the type of scatterers that cause the radar returns. The scatterers can be hydrometeors, biologicals, or earth-sourced. The ability to reliably interpret the radar-sensed thermodynamic phase of the hydrometeors (solid, liquid, mix) in the context of cloud microphysics and precipitation physics makes it possible to assess the icing hazard potential to aviation. That assessment for Federal Aviation Administration (FAA) purposes would necessarily be performed by automated algorithms based in hydrometeor classification terms. The truth as to the icing hazard aloft (where the radar scans) is required to ascertain the value of such algorithms. The Buffalo Area Icing and Radar Study (BAIRS) of 2013 was a partnership between MIT Lincoln Laboratory (LL) and the National Research Council of Canada (NRC) to perform in situ icing missions within the surveillance range of the dual polarization NEXRAD in Buffalo, NY. The goal of these 2013 missions, and the subject of this report, was to target specific winter weather scenarios known to exhibit an aviation icing hazard for the purpose of quantifying the microphysical properties of the target zones and verifying the presence of supercooled liquid water (SLW) to support validation of hydrometeor classification algorithms. These are the first such missions to execute in situ measurements within a NEXRAD's surveillance range running with the fielded, operational NEXRAD hydrometeor classifier. NRC's Convair-580 instrumented research plane was used for three icing missions covering 14 hours. Three distinctly different winter weather scenarios were encountered. This document details the analysis of in situ data such as particle type and liquid water content (LWC) with NEXRAD dual polarization parameters for the three missions. The BAIRS analysis identified these key findings: -NEXRAD radar returns are prevalent in conditions of supercooled water, -NEXRAD classification shows positive results based on particle imagery, -NEXRAD "dry snow" class masks the presence of mixed phase potential icing hazard, -NEXRAD "unknown" class contains diverse regions of icing hazard potential, and there are methods to classify some of these regions, and -In situ aircraft observations are an important tool to both verify algorithm performance and guide further development.