Laboratory experiments on the effect of organic acids and metals on the charge transfer during ice crystal – graupel collision under the conditions similar to stratiform clouds

Abstract

Abstract. Laboratory investigations have been carried out to find the sign and magnitude of charge transfer during the collision between ice crystals and graupel in the presence of supercooled water droplets inside the cylindrical steel chamber kept inside a walk-in cold room, which can reach a temperature of −30 °C. The experiments were performed with pure water (Milli-Q, 18.2 Megohms-cm) and with trace amounts of organic acids and metals at low Rime Accretion Rate (<0.40 g m−2 s-1) applicable to stratiform clouds in the temperature range −5 to −27 °C. The ice crystals and supercooled droplets collided with the graupel target at a constant impact velocity of 2.2 m/s. The presence of trace chemicals (organics or metals) saw significant increase in the magnitude of charge transferred per crystal collision to the graupel. These experiments therefore suggest that the presence of trace amounts of organics or metals in cloud water can significantly alter the electrical structure of stratiform clouds.

Air Masses and Weather Types: A Useful Tool for Characterizing Precipitation Chemistry and Wet Deposition

“…Sources of these acids include both anthropogenic and biogenic emissions. Biomass burning, soil, traffic, vegetation, in-cloud process or oxidation from precursor compounds in the gas phase have been identified such as possible sources (Kawamura et al, 1985;Keene and Galloway, 1988;Talbot et al, 1988;Grosjean, 1989;Avery et al, 1991;Gradel and Crutzen, 1993;Willey and Wilson, 1993;Kumar et al, 1996;Guenther et al, 2006;Prakash and Kumar, 2010;Zhang et al, 2011). It has been estimated that organic acids contribute between 25% and 65% of the rainwater acidity in industrial and urban areas (Yu et al, 1998;Altieri, 2009) and this contribution is higher in remote areas (Galloway et al, 1982, Likens et al, 1987, Andreae et al, 1988Yu et al, 2009).…”