In-flight icing hazards from supercooled small drops, drizzle and freezing rain pose a threat to all aircraft.Several products have been developed to provide hazard warning of in-flight icing to the aviation community. NCAR'sCurrent Icing Product' (CIP) was developed to provide a near-realtime assessment of the hazard presented bysupercooled liquid water (SLW) aloft in an algorithm that combines data from satellites, the Rapid Update Cycle (RUC)model, the national 2-D composite of S-band NEXRAD radar reflectivity, surface observations and pilot reports(PIREPs). NIRSS2 (Fig. 1) was developed by NASA to provide a ground-based, qualitative in-flight icing hazardassessment in the airport environment with commercially available instrumentation. The system utilizes a multichannelradiometer3, built by Radiometrics Corporation, to derive the temperature profile and integrated liquid water (ILW).NIRSS's radar is a modified airborne X-band model WU-870 made by Honeywell. The ceilometer used is a standardVaisala CT25K Laser Ceilometer. The data from the vertically pointing ceilometer and X-band radar are only used todefine the cloud bases and tops. The liquid water content (LWC) is then distributed within the cloud layers by thesystem software. A qualitative icing hazard profile is produced where the vertical temperature is between 0 and -20°Cand there is measurable LWC.
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