Ice and water content of stratiform mixed-phase cloud

Spatial characterization and probability distribution of particles in stratiform mixed-phase clouds in the temperature range 5 to -45 degrees C were investigated based on 81 hours of flight on the NCAR C-130 during the Alliance Icing Research Study II. Cloud particles were video-recorded impacting on the optical window of a cloudscope, and Liquid Water Content (LWC) and Ice Water Content (IWC) derived from measurements of the power to evaporate particles of different size, shape and density collected by the T probe constant temperature sensors. Data were recorded at 1 Hz for a resolution of 130 m. Transitions between liquid, glaciated and mixed-phase regions were sharp, frequent supercooled liquid re-ions lasted less than 2 seconds (<260 m), while less frequent mixed-phase and glaciated regions persisted between 2 and 300 seconds (0.26 to 39 km) along the aircraft track. LWC, IWC and Total Water Content (TWC) were measured in concentrations up to 1.25, 0.45 and 1.25 g m(-3) with an uncertainty of similar to 0.02 g m(-3). The IWC/TWC ratio showed two maxima at mostly liquid (<0.1) and mostly ice (>0.9); mixed-phase corresponded to about 40% of the measurements. The large T probe showed mixed-phase clouds with ice fraction less than half at temperatures below -20 degrees C, while the small T probe measured higher ice proportion, suggesting that ice was present in the form of preferentially collected small particles. At high temperatures (>-15 degrees C) ice and water were measured in concentrations up to 0.2 and 0.6 g m(-3) respectively; at temperatures below -20 degrees C they were both measured in concentrations up to 0.3 m(-3). Copyright (C) 2009 Royal Meteorological Society