Experimental measurements of the collection efficiencies of ice crystals in electric fields

✍ Scribed by J. Latham; C. P. R. Saunders

• Publisher: John Wiley and Sons
• Year: 1970
• Tongue: English
• Weight: 789 KB
• Volume: 96
• Category: Article
• ISSN: 0035-9009
• DOI: 10.1002/qj.49709640808

✦ Synopsis

Abstract

Experimental studies have been made of the aggregation of ice crystals of mean diameter about 5 μm upon an ice sphere of diameter 0.2 cm at the same temperature. The growth rate was found to be roughly independent of temperature over the range − 7°C to − 27°C and increased with electric field strength E to exceed the field‐free value by about 15 per cent, 40 per cent and 80 per cent in fields of 500, 1,000 and 1,500 V cm^−1^ respectively. At higher values of E the growth‐rate was reduced because of the ejection of clusters of ice crystals from the aggregate, probably under the influence of the intense electric forces. An appreciable amount of aggregation was observed at temperatures as low as − 37°C, in the presence or in the absence of electric fields.

Absolute values of collection efficiencies at a velocity of 3 m s^−1^ were determined at the temperatures − 7°C, − 11°C, − 17°C and − 27°C. In the absence of an electric field collection efficiencies of about 0.3 were determined at all temperatures studied. Experiments with charged ice crystals indicated that electric fields increase the growth rate by increasing the adhesion efficiency and not the collision efficiency.