The effect of cloud droplet spectrum on electrical charge transfer during individual ice-ice collisions

PEREYRA, RODOLFO GUILLERMO; AVILA, ELDO EDGARDO; CARANTI, GIORGIO; AGUIRRE VARELA, GUILLERMO GABRIEL

Alabama

Conferencia; 11th International Conference on Atmospheric Electricity (ICAE); 1999

International Commission on Atmospheric Electricity

New experiments were performed with a wind tunnel in a cold room in arder to investigate theint1uence of the cloud droplet spectrum on the charges transfen'ed during ice-ice collisions. A fixed artificialgraupel growing by riming, placed inside a wind tunnel, is collided by ice spheres. The experiments wereperformed using two different cloud droplet spectrum; the ice spheres used were of about 100 ¡J,min diameter; theimpact velocity around 4 m S.l. The ambient temperature (Ta) was varied in the range -10 to -30°C. The effectivewater content EW, was between 0.2 and 1.1 g m.3. The results show that the predominant sign of the chargetransfer for a set of given conditions is dependent on the cloud droplet spectrum which means that the charge signreversal temperature is also a function of the spectrum. In particular, using smaller droplets, the' reversal signoccurs below -25°C, while for larger droplets the reversal sign is produced at -18°C. These results show that thedroplet spectrum is an important parameter to keep under control when natural cloud conditions are beingsimulated.