Airborne measurements of the concentration of natural and artificial freezing nuclei

Abstract

Abstract An aircraft‐mounted instrument for measuring the concentration of freezing nuclei in the free atmosphere is described. It has been calibrated and its limitations investigated. Preliminary observations, in flight, of natural freezing nuclei were made. The temperature at which a given concentration of ice crystals formed on natural nuclei varied markedly from day to day, and increased with altitude. Measurements in flight of the concentration of freezing nuclei in silver‐iodide smoke, released from a ground generator, are described. The nucleating properties of small particles produced by a hydrogen burner deteriorated very rapidly, while larger particles produced by a kerosene burner were more durable.