In-flight icing hazard: electromagnetic analysis for dual polarization radar detection

In a meteorological adverse conditions scenario, surely in-flight icing represents a real danger, originating aerodynamics instability due to ice accretion on the aircraft surfaces, malfunctions of on-board devices caused by antennas freezing, and problems on the air- craft engines due to the reduction of the temperature in the air combustion process. The in-flight icing hazard is due not only to the presence of some specific ice crystals, but also to the physical conditions that allow the icing formation and growth of ice. In this context, a relevant phenomenon is the formation of Super-Cooled Liquid Water Droplets (SCLWD), micrometric droplets of liquid water surviving at temperature well below 0C, in a meta-stable state able to suddenly freezing at a minimal perturbation. The SCLWDs can indeed create a very solid thin layer of ice particles on the aircraft structures where ice crystals can further stick and grow up the ice layer on the critical structure of the aircraft on its own. The problem is that this phenomenon happens very quickly so that aircraft de-icing devices are unable to counteract it promptly with a consequent sudden loss of aerodynamics and aircraft lift. The dual-polarization radars are helpful in the detection of adverse atmospheric condi- tions and providing useful information also about the nature of a phenomenon under ob- servation, therefore a study about their capabilities and related methods in ice detection has been carried out. A range of polarimetric signature values for the icing conditions has been produced by using the POWER simulator: the most similar process to the ice crystal scattering simulated by POWER is the snow aggregates scattering process. The results obtained from the POWER simulator show values of reflectivity and di↵erential reflectivity in agreement with the real data provided by a polarimetric weather radar. The results of dual-polarization detection of the presence of icing condition are based on data from the CHILL Polarimetric Dual Band Doppler Radar (S-band, X-band) and the NASA D3R dual-frequency (Ku-band and Ka-band), dual-polarization Doppler radar, developed for the ground validation program of the NASA/JAXA Global Precipitation Measurement (GPM) mission at Colorado State University. In the analyzed meteorolog- ical scenarios, values of reflectivity (Z) and di↵erential reflectivity (Zdr) are highlighted allowing to infer the presence of SCLWD. Furthermore, the values of cross correlation coecient (⇢hv) and specific di↵erential phase (Kdp), and a scatter plot of Z vs Zdr are analyzed to verify the eciency in icing detection. This detection method is compared to other results presented in literature and its outcomes are consistent with the values of temperature measurement at Denver meteorological station.