1. That branch of the study of atmospheric electricity concerned with the electrical charge carried by precipitation particles and with the manner in which these charges are acquired. 2. The electrical charge borne by precipitation particles. A very complex and highly variable picture is obtained when charges are measured on individual raindrops or snow crystals and no present theory approaches a complete explanation of all details. In general, more raindrops are positively than negatively charged. Sometimes the prevailing sign of the charges even shifts in the course of a given storm's lifetime. See precipitation current; Compare ion-capture theory.