Characterizations of Aircraft Icing Environments that Include Supercooled Large Drops

Measurements of aircraft icing environments that include supercooled large drops (SLD) greater than 50 mm in diameter have been made during 38 research flights. These flights were conducted during the First and Third Canadian Freezing Drizzle Experiments. A primary objective of each project was the collection of in situ microphysics data in order to characterize aircraft icing environments associated with SLD. In total there were 2793 30-s averages obtained in clouds with temperatures less than or equal to 08C, maximum droplet sizes greater than or equal to 50 mm, and ice crystal concentrations less than 1 L21. The data include measurements from 12 distinct environments in which SLD were formed through melting of ice crystals followed by super-cooling in a lower cold layer and from 27 distinct environments in which SLD were formed through a condensation and collision–coalescence process. The majority of the data were collected at temperatures between 08 and 2148C, in stratiform winter clouds associated with warm-frontal or low pressure regions. For in-cloud mea-surements with temperatures less than or equal to 08C, the relative fraction of liquid-, mixed-, and glaciated-phase conditions were 0.4, 0.4, and 0.2, respectively. For each 30-s (3 km) measurement, integrated drop spectra that spanned 1–3000 mm were determined using measurements from forward-scattering spectrometer probes and 2D-C and 2D-P probes. The integrated liquid water content (LWC) for each drop spectrum was compared with