NEXRAD Correction of Vertically Integrated Liquid in Areas of Partial Beam Blockage

The FAA requires an accurate depiction of weather occurring across the CONUS for the safe routing of air traffic within the national airspace. Vertically integrated liquid (VIL) is estimated from reflectivity data and displayed to air traffic controllers to help identify the severity of potential weather hazards to aircraft. Factors such as partial beam blockage and melting layer contamination affect the accurate depiction of VIL as reflectivity is reduced in the former case and enhanced in the latter. In mountainous areas of the CONUS where partial blockage of the beam occurs more often, VIL is often reduced and could cause potential safety issues when routing air traffic. With the upgrade of the NEXRAD radar network to dual polarization, additional data products can be leveraged to compensate for these blockage effects. Differential phase, a new data product, is more immune to radar miscalibration and blockage of the beam. A new technique developed by the National Severe Storms Laboratory uses a combination of differential phase and reflectivity to compute specific attenuation along a radial. Liquid water content can then be computed directly from specific attenuation to obtain a more accurate estimate of VIL. This paper describes the algorithm and a comparison of the modified product with the original VIL product in the NEXRAD Open Radar Product Generator environment.

This work was sponsored by the Federal Aviation Administration under Air Force Contract No. FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government.