THE DECAY OF ICE-NUCLEATING PROPERTIES OF SILVER IODIDE IN THE ATMOSPHERE

Abstract

Finely divided zinc sulfide and freezing nuclei in the form of silver-iodide smoke were released from separate generators at the same time from the same position on the ground. Both were detected simultaneously at distances up to 56 kilometers downwind from the respective generators, by apparatus installed in an aircraft. The comparative concentration was used as a measure of the deterioration in the ice-nucleating properties of the silver iodide. The total number of freezing nuclei, effective at ?17C, in silver-iodide smoke from a hydrogen burner, decreased by a factor of ten after eight minutes of exposure in the free atmosphere. The corresponding time with use of a kerosene burner was 50 minutes. The rate of decrease in the number of freezing nuclei was not influenced by the cloud cover.