Charge transfer measurements during single ice crystal collisions with a target growing by riming

Abstract

Direct measurements of the electric charge separated from individual collisions between vapor grown ice crystals and an artificial graupel growing by riming have been made in the present laboratory work. The measurements were performed with an impact velocity of 8.5 m s-1, the ambient temperature was varied in the range -5 to -20°C, the average ice crystal sizes between 20 to 40 μm, with an effective liquid water content up to 1.5 g m-3. The magnitude of the charge separated per collision is on the order of 10 fC, and the sign of the average charge depends on the ambient temperature for the present EW. We found that the artificial graupel charges positively for temperatures above - 12°C and negatively for temperatures below - 14°C. The current results are compared with those obtained by other authors that used the multiple crystal collision technique. Copyright 2002 by the American Geophysical Union.