An improved Millipore filter technique for measuring the concentrations of freezing nuclei in the atmosphere

Abstract

Abstract A technique to measure the concentration of freezing nuclei in the atmosphere is described. It is a development of the Millipore filter method described by Bigg, Mossop and Heffernan (1961), from which many of the difficulties experienced by them and other workers in the field have been eliminated. The main advantages which this technique has over others using Millipore filters are as follows: the ability to work at relatively low and controlled supersaturations; the ability to activate large numbers of nuclei on the filter without the crystals interfering; the finding of a linear relationship between the number of nuclei detected and the volume sampled, except in very dusty conditions; an improved reproducibility.