Ice nucleus concentrations in Seoul were measured using millipore filters for the period of last four winters, 1962-1963, 1963-1964, 1964-1965 and 1965-1966.
Concurrently, the microscopic dust count and the radioactivity of air borne dust caught on the filter surface were also examined.
Taking into consideration the correlation among these factors, the sources of ice nuclei in Korea seem to be distant rather than local.
The average value of ice nucleus concentrations in Seoul during the winter seasons was 0.12/l at -15°C, which is somewhat lower than the Australian average and also that of Japan.