In Situ Measurements of Charge on Cloud Drops

A unique instrument has been developed to measure the average charge on cloud drops. The charge per unit time on the stream of residue from evaporated cloud drops is captured by a filter in our instrument and used along with the concentration of the particles to determine the average charge on the particles and thus the cloud drops. The stream of cloud drop residues is produced by a Cloud-drop Virtual Impactor (CVI). The average cloud drop charge as a function of time was measured during C130 flights in the ICE-L field program. Almost all clouds contained drops with significant charge. Important potential consequences of the charge observed on cloud drops will be presented.