Airborne W-band Radar Measurements of Winter Clouds

This paper presents an analysis of airborne radar and in-situ data collected during the second Alliance Icing Research Study (AIRS II). AIRS II was conducted between November 2003 and February 2004 over the Mirabel airport near Montreal, Canada and the surrounding regions in Ontario and Quebec. AIRS II was an international collaborative aircraft icing study using arrays of ground-based and airborne in-situ and remote-sensing instruments. During AIRS II, the University of Wyoming Cloud Radar (WCR) was installed on the National Research Council of Canada Convair-580 (CV580) research aircraft during the Nov-Dec 2003 period. The WCR operated either in a dual-polarization mode using a side-looking antenna or in a single-polarization mode using a side-looking and a nadir-looking antennas. The dual-polarization mode provided horizontal structures of polarimetric radar observables (Z, ZDR and LDR), while the dual-antenna radar configuration provided simultaneous vertical and horizontal cross-sections of radar reflectivity and Doppler velocity. Based on the in-situ cloud microphysics data and the radar measurements from the nearest usable range gates, the polarimetric radar signatures of different hydrometeor types were identified. For example, supercooled drops generally have weak Z and zero ZDR and no detectable LDR, while pristine ice crystals have high ZDR (>3 dB) values. The radar signatures identified from the in-situ and radar analyses are then used to determine the frequency of occurrences of different particle types (pristine ice crystals, ice aggregates, rimed crystals, melting crystals, supercooled cloud drops, drizzle and rain) in the winter clouds sampled during AIRS II.