Charge separation in thunderstorm conditions

PEREYRA, R. G.; BURGESSER, R. E.; E. E. AVILA

JOURNAL OF GEOPHYSICAL RESEARCH

Año: 2008 vol. 113 p. 1 - 12

0148-0227

A laboratory investigation of the electric charge transfer in collisions between vapourgrown ice crystals and a riming target is presented in this work. A series of experimentswere conducted for ambient temperatures between –8°C and –29°C, air velocity of 8 ms-1 and effective liquid water content from 0.5 to 10 g m-3, with the goal of studying theperformance of the non-inductive mechanism under a wide range of temperature andliquid water content. At low temperatures (below –19oC), the results revealed nodependence of the charge separated per collision upon variations of the liquid watercontent. While at temperatures above –19oC, the efficiency of the graupel chargingcould decrease as the liquid water content increases, as a consequence of the decrease ofthe probability that the ice crystals impact and rebound from the graupel surface in thedry growth regime. We found that the dominant sign of the graupel charging wasnegative for temperatures below –15oC and positive at higher temperatures. A simplefunctional representation of our laboratory results is given so that they can beincorporated in cloud electrification models.