Results of Five Years' Observations of Cloud Nucleus Concentration at Robertson, New South Wales

Abstract

Cloud nucleus concentration measurements made at hourly intervals between 1968 and 1973 at Robertson, N. S. W., show a very clear diurnal pattern with a maximum at approximately 1800 local time and a minimum at 0600 local time. It is suggested that photochemical reactions play a major role in the generation of cloud nuclei. A close examination of the data suggests that the long-term trend, while indicating a general increase in pollution levels, could as readily be interpreted as fluctuations with changes in local or global meteorological factors. A much greater period of observation would be required to decide the question.