A. Wegener (1911) was the first to suggest that the atmosphere
might contain nuclei upon which sublimation (deposition
) of water vapor
directly to ice
occurs in a manner similar to condensation
upon condensation nuclei
. In experiments where various nuclei are added to supercooled clouds
, it is generally difficult to determine whether these nuclei function as deposition nuclei
or as freezing nuclei
. It has never been demonstrated that natural deposition nuclei (as distinguished from freezing nuclei) exist in the atmosphere. In the laboratory, cases of artificial preparation of true sublimation nuclei have been reported that activate ice crystals without reaching anywhere close to water saturation
; lack of such nuclei in the atmosphere
results from the predominance of mixed nuclei
Wegener, A. 1911. Thermodynamik der Atmosphäre. Barth, Leipzig.
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