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How well do we understand deposition ice nucleation?
02.07.2019, 15:00 - 16:00
KIT, CN, IMK, Geb. 435, Raum 2.05

Deposition ice nucleation is one of the so called modes of ice nucleation that may have relevance e.g. in the formation of cirrus clouds. It is thought that deposition nucleation occurs via direct deposition of water vapor into the ice phase on the surfaces of water insoluble particles, although some researchers have also suspected that an intermediate liquid phase occurs in the process. Hoose and Möhler pointed out in their 2012 review paper that with various ice nucleating particle types, the experimental temperature dependence of the critical supersaturation S* of deposition ice nucleation has a U-shape, i.e. at high temperatures (above about 240 K) S* decreases with lowering temperature, but at low temperatures (below about 220 K) the trend is reversed. Such a behavior suggests that  there might be two different mechanisms at work, one at high temperatures and the other at low temperatures. In order to study the temperature dependence systematically, we have measured the critical supersaturations of several different particle types, including metal oxides, cloud seeding materials mineral and soil dusts, and different fly ashes, in the temperature interval 208 – 253 K

using a modified SPIN instrument. We find that the steepness of the temperature dependences vary greatly depending on particle types, with some particles showing the U-curve and others exhibiting only the left branch of the U in the whole temperature interval. The results are interpreted using the recently developed adsorption nucleation model.

Diese Veranstaltung ist Teil der Reihe Karlsruher Meteorologisches Kolloquium
Prof. Ari Laaksonen

Finnish Meteorological Institute, HELSINKI
Institut für Meteorologie und Klimaforschung (IMK-AAF)
Hermann von Helmholtzplatz 1
76344 Eggenstein-Leopoldshafen
Tel: 0721-608-23943
Fax: 0721-608-24332
E-Mail:susanne bolzRzj1∂kit edu
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