Measurement of electric charge of cloud droplets, drizzle, and raindrops

The purpose of this review is to survey recent work on the electricity of cloud droplets, drizzle, and raindrops and, in particular, to describe the instruments used in such observations. The review begins with a number of basic definitions and key questions in this area of cloud physics. A detailed description of instruments for the measurement of drop size and charge, both at the ground and in clouds, follows. The third section presents and interprets some of the data gathered with these instruments. We then sketch ongoing attempts to observe the charge distribution of the particles in relation to the cloud life cycle and to determine the size range of the particles that constitute the main charge carrier in the cloud. We conclude with a statement of three current goals of investigation.