Self‐charging of melting ice

Publisher Website
Google Scholar
Abstract
A brief laboratory investigation was initiated to try to duplicate a phenomenon which had been repeatedly observed in certain flight measurements during the Flagstaff cumulus studies: the apparent strong negative charging of ice hydrometeors in the final stage of melting during their fall outside of the cloud. Sample ice structures of 1 cm3 from distilled water were melted in an 8 m sec−1 air stream at ambient temperatures. Regardless of the technique of measurement used (current into the sample, charge into the sample, or charge into an open Faraday cage around the sample), certain features were observed consistently: (a) a positive charge was acquired by the sample, (b) the magnitude of the charge was of the order of 30 picocoulombs (0.1 esu), and (c) the acquisition of charge occurred primarily during the later portion of the melting process. Generally similar but more erratic results were obtained with actual hail samples.The sign of the charging was opposite to that observed in the flight measurements, and the magnitude of the charging was far less, but the correlation of the charging with the final stage of melting agreed with the results of the flight tests. Careful laboratory tests previously reported by Dinger and Gunn also showed positive charging during melting, and the charging correlated with the amount of dissolved gas and hence bubbles. It is felt that the charging effect is real and is probably primarily associated with effects from bubbles during melting, and that the disagreement in sign and magnitude between the laboratory and flight measurements may be attributable to the large differences in ambient conditions and differences in the physical and chemical properties of the hydrometeors.

This publication has 7 references indexed in Scilit: