Introduction Radar detection of in-flight icing is difficult

1. Towards the Detection of Aircraft Icing Conditions Using Operational Dual-polarimetric RadarScott Ellis1, David Serke1, John Hubbert1, David Albo1, Andrew Weekly1, Marcia Politovich1, Andrew Gaydos1, Daniel Adriaansen1, Earle R. Williams2, David J. Smalley2, and Michael F. Donovan21. National Center for Atmospheric Research,2. MIT Lincoln Laboratory • Icing Hazard Level Algorithm (IHLA) • Stand-alone, real-time • Modular design • Three icing detection modules • Freezing drizzle based on Ikeda et al. (2009) – modified to identify SLW above surface – FRZDRZ • Mixed phase based on Plummer et al. (2010) – SLW • Indirect measurements based on Williams et al. (2011) – prototype, not yet implemented in real-time code – HZDRA • Introduction • Radar detection of in-flight icing is difficult • SLW radar signature overlaps with that of ice • Mixed phase radar signature dominated by ice particles • Dual-pol signatures alone not sufficient to detect SLW • What about statistical properties of data? • Freezing Drizzle detection by Ikeda et al. (2009) • Spatial texture of reflectivity (Z) • Freezing drizzle has smoother Z than snow • Mixed phase cloud detection • Mean of Zdr and Kdp greater in ice only • Variance of Zdr and Kdp greater in ice only • Indirect measurements have shown promise • Use radar signatures of riming dendrites that form in water saturated regions containing SLW - described in Williams et al. (2011) • These dendrites have distinguishable radar signatures • Data • IHLA run using CSU-CHILL radar and RUC model data • NIRSS (NASA Icing Remote Sensing System) • Pilot icing reports (PIREPS) • Data collected from December 2010 to June 2011 – 22 cases (both with and without icing) observed CSU-CHILL Experiment Design NIRSS • Results • IHLA for a non-icing and an icing case compared • Only FRZDRZ and SLW modules • Icing (ILW) measured independently by NIRSS • Prototype HZDRA applied to icing case • Not identified as icing by FRZDRZ or SLW • New module successfully identifies icing conditions Reflectivity, dBZ Differential reflectivity, dB Non-icing Icing Reflectivity, dBZ Reflectivity, dBZ HZDRA fuzzy logic output Acknowledgements 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. The National Center for Atmospheric Research is sponsored by the National Science Foundation. Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Fuzzy logic output above NIRSS site Fuzzy logic output above NIRSS site > 0.5 indicates icing detection > 0.5 indicates icing detection