Abstract
Concentrations of ice nuclei have been measured in aerosols sampled by pairs of membrane filters mounted high on the forward mast of a ship making almost continuous voyages during the years 1969–72 over the half of the Southern Hemisphere centered on Australia. Comparison with land-based concentrations made by a similar method rule out the possibility that the nuclei are of purely continental origin. Nucleus concentrations were found to be highest in a band centered on latitude 40S, and it is suggested that they are transported from a distant land source, or from a stratosphere source, and brought to sea level by convective mixing or other air interchanges.
