Estimation of Aircraft Icing Intensity Using Z-LWC Relationship from Radar and Aircraft Data

Aircraft icing, a hazardous phenomenon involving the accumulation of ice or supercooled water droplets on an aircraft’s wings and airframe in freezing temperatures when an airplane flies through clouds, poses substantial risks to aviation safety. From a meteorological perspective, aircraft icing is determined by the air temperature, and the number and size of water droplets. In particular high values with water contents are a crucial factor correlating with increased icing intensity. Since weather radar can detect ice and water droplets larger than 2 mm in diameter within precipitable clouds, we have developed two radar-based aircraft icing products (icing potential areas and icing intensity) to facilitate safe aviation services in real-time. 

In this study, the estimation algorithm of aircraft icing intensity using Z-LWC relationship was presented. We utilized data from a ground-based S-band radar mosaic, an icing detector, and a cloud droplet probe installed on the aircraft (KMA/NIMS atmospheric research aircraft; NARA) for 13 cases of icing. Within the icing areas determined by the icing detector, 3-dimensional gridded reflectivity (Z) and liquid water content (LWC) were matched based on time and location. A Z-LWC relationship was then derived using the paired dataset sorted by size. We calculated LWC from Z using this relationship and categorized icing intensity into Trace, Light, Moderate, Heavy, and Severe, according to FAA criteria (FAA 2001). The estimation of icing intensity was solely focused within the identified icing potential areas (Kim et al. 2023). The algorithm was validated using a “Light” intensity icing case from aircraft report (AIREP), showing good performance, but further verification is needed. 

ACKNOWLEDGEMENTS
This research was supported by “Development of integrated radar analysis and customized radar technology (KMA2021-03021)” of “Development of integrated application technology for Korea weather radar” project funded by the Weather Radar Center, Korea Meteorological Administration.
This work was funded by the Korea Meteorological Administration Research and Development Program "Developing Application Technology using Atmospheric Research Aircraft" under Grants (KMA2018-00222).