Charge separation during the fragmentation of rime and frost

Charge Separation Mechanisms in Clouds

“…Charge transfer associated with surface growth or sublimation has been noted by everyone who has worked in the area of collisional ice charging in clouds. The relative growth rate theory discussed below, has its origins in the often observed result that growing ice surfaces charge positively, while sublimating ice surfaces charge negatively, as noted by Findeisen (1940), Findeisen and Findeisen (1943), Buser and Aufdermaur (1977), Marshall et al (1978), Gaskell and Illingworth (1980), Jayaratne et al (1983), Rydock and Williams (1991), Caranti et al (1991), Dong and Hallett (1992), Saunders et al (1993), Scavuzzo et al (1995) and Mason and Dash (2000). Most of these experiments were carried out by artificially cooling or heating an ice surface while its surface was removed by collisions or by fragmentation, thus the laboratory simulations are not representative of the conditions in real clouds.…”

“…Figure 11 represents the case of a faster growing ice crystal rebounding from a slower growing graupel pellet, so that the charge and mass exchange during the collision results in the graupel becoming negatively charged. 2000), · · · · · · Takahashi (1978), -- Saunders and Peck (1998) Figure 12 shows laboratory results from Saunders et al (2006) together with those from Pereyra et al (2000), Takahashi (1978) and Saunders and Peck (1998). Plotted on these graphs are the critical values of temperature and cloud effective water content for which the charge transfer during crystal/graupel collisions is zero.…”

“…The laboratory studies of Pereyra et al (2000) provided the breakthrough-they mixed ice crystals into their droplet cloud just before the mixed cloud impacted on the riming target. The studies of Saunders and Peck (1998) however, were performed in a chamber in which the ice crystals grew in the same chamber as the droplets. The importance of the cloud conditions for particle growth was investigated in studies by Saunders et al (2006) whose data line is shown in Fig.…”