An investigation into the properties of atmospheric freezing nuclei and sea-salt nuclei under maritime conditions at the West Coast of Ireland

Summary Parallel measurements of the concentration of freezing nuclei and sea-salt particles carried out on the west coast of Ireland during summer 1958 to study the activity of sea-salt particles in the process of ice-nucleation of supercooled clouds are described and discussed. The results indicate that the concentration of freezing nuclei, active above –30°C, has no relationship to that of the sea-salt particles. A pronounced increase of the freezing nucleus concentration was observed during advection from the mainland showing that even under maritime conditions the most active freezing nuclei are particles of continental origin.

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Zusammenfassung Es wird über parallele Messungen der Gefrierkerne und der Seesalzkerne berichtet, die im Sommer 1958 an der irischen Westküste durchgeführt wurden, um die Wirkung der Seesalzkerne für den Gefrierprozess in unterkühlten Wolken zu studieren. Die Ergebnisse zeigen, dass zwischen der Konzentration der im Temperaturbereich zwischen 0°C und –30°C aktiven Gefrierkerne und den Seesalzkernen keinerlei Beziehung besteht. Eine starke Erhöhung der Gefrierkernzahl bei Advektion von Aerosolen vom Festland deutet an, dass auch unter maritimen Bedingungen, Teilchen kontinentaler Herkunft besonders aktive Gefrierkerne sind.

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Dedicated to Senior ProfessorL. W. Pollak, Ph. D., M.R.I.A. on his seventieth birthday.

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The research reported in this article has been sponsored and supported in part by the Geophysics Research Directorate of the Air Force Cambridge Research Center. Air Research and Development Command, United States Air Force, under Contracts AF 61(052)-26 and AF 61(514)-927, through the European Office, ARDC in Brussels.