Measurements of Natural Freezing Nuclei at High Altitudes

Abstract

A NUMBER of determinations of freezing nuclei has been made in aircraft. These form part of a programme of investigation into (a) the distribution and properties of freezing nuclei at high altitudes (where they are thought to play a part in the formation of rain by the Bergeron process), and (b) the question of whether the rainfall singularities reported by Bowen¹, and attributed by him to the arrival in the lower atmosphere of meteoritic dust, are accompanied by corresponding fluctuations in the concentration of freezing nuclei. Daily measurements were made near Sydney, Australia, during January 1954 and January 1955, and near Tucson, Arizona, United States, in January 1955. In addition, in January 1955 measurements using a somewhat similar method were carried out on a mountain top in the Hawaiian Islands. The results to date are summarized below. The month of January was chosen because the meteor dust – rainfall hypothesis was based on statistics for that month.