Ice and water content of stratiform mixed‐phase cloud

Abstract

Spatial characterization and probability distribution of particles in stratiform mixed-phase clouds in the temperature range 5 to −45 • 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 regions 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 ∼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 • 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 • C) ice and water were measured in concentrations up to 0.2 and 0.6 g m −3 respectively; at temperatures below −20 • C they were both measured in concentrations up to 0.3 g m −3 .

Observed Southern Ocean Cloud Properties and Shortwave Reflection. Part I: Calculation of SW Flux from Observed Cloud Properties*

“…However, in reality the situation is likely complicated beyond the two simple cases we have presented here by feedbacks between the presence of ice, precipitation, cloud dynamics, aerosol scavenging, and cloud coverage as described by Morrison et al (2011) and Berner et al (2013). It is possible that in a case where CCN does not change drastically the constant r e case might be more accurate given the occurrence of small regions of pure liquid and ice in mixed phase (Grosvenor et al 2012;Vidaurre and Hallett 2009). These two simple cases are selected to indicate the radiative impact of the liquid to ice transition in low cloud in the Southern Ocean and demonstrate the importance of constraining the microphysics during such transitions.…”

HoloGondel: in situ cloud observations on a cable car in the Swiss Alps using a holographic imager

“…In situ measurements of the structure and the microphysical properties of clouds are important to gain a better knowledge of the radiative properties and the development of clouds (e.g., Sun and Shine, 1994;Morrison et al, 2012). Commonly these measurements are performed with a research aircraft (e.g., Verlinde et al, 2007;Vidaurre and Hallett, 2009;Heymsfield and Willis, 2014;Lawson et al, 2015), a helicopter (e.g., Siebert et al, 2006), a tethered balloon system (TBS) (e.g., Lawson et al, 2011;Sikand et al, 2013) or at mountain-top research stations (e.g., Rogers and Vali, 1987;Uchiyama et al, 2014;Geerts et al, 2015;Vochezer et al, 2016). This paper introduces a novel approach for measuring in situ properties of clouds on a cable car.…”

Airborne Measurement of Liquid and Total Water Content

“…The significance of this breakup effect is still to be determined. The relative impact kinetic energy to surface energy ratio (E K /E s ), given by a modified Weber number L, characterizes the breakup process (Hallett and Christensen 1984;Vidaurre and Hallett 2009b). For convenience, E s is defined as the surface energy of a spherical particle; thus, L is given by…”

“…Aircraftmounted probes, limited by instrumental resolution, revealed narrow mixed-phase regions on the order of a few hundred meters and less (Vidaurre and Hallett 2009a). These probes have been individually tested and calibrated in the laboratory, and as part of a normal procedure they are referenced to clear-air conditions in each flight.…”