Development of Dual Polarization Aviation Weather Products for the FAA

Weather radar products from the United States' NEXRAD network are used as key components in FAA weather systems such as CIWS, ITWS, and WARP. The key products, High Resolution VIL (HRVIL) and High Resolution Enhanced Echo Tops (HREET), provide primary information about precipitation location and intensity. The NEXRAD network will become dual polarization capable beginning in late 2010 adding the ability to classify hydrometeors. This new aspect from radar remote sensing of the weather offers opportunity to provide new aviation weather products and augment existing ones.

This paper will detail the dual polarization product development program at MIT Lincoln Laboratory (LL) in support of FAA system needs. Current development efforts focus on four products. Two new products will provide volumetric analysis seeking aviation hazards (icing and hail). Two existing products, HRVIL and HREET, will be invigorated by dual polarization data to yield improved data quality and mitigation of partial beam blockage. The LL program has partnered with NCAR and NSSL subject matter experts to bring their most advanced research results into these new and improved products. The LL program also has partnered with Valparaiso University for them to provide dual polarization and local sonde sounding data especially during suspected icing conditions.

The new Icing Hazards Level (IHL) product is expected to provide the most benefit to the FAA. Its development also poses the greatest challenge both in scope and in the ability of S-band radar to sense the phenomena of interest. Icing phenomena include supercooled drops/droplets and ice crystals and the associated aviation hazard could be aloft or near/at the surface. Graupel is an indication that supercooled water has accreted to ice particles. The initial NEXRAD hydrometeor classifier will not have an explicit supercooled water class or the benefit of supporting data. It will have ice crystal and graupel classes. The LL approach will utilize at least some additional data (vertical thermodynamic profiles). Techniques applied to the development of IHL will likely have applicability to the other products as well. Aspects of the IHL development will also be discussed in the paper.