Dr. Ulrich Bundke

Institute for Atmosphere and Environment, J.W. Goethe

University

Frankfurt, Germany

Ice nuclei (IN) initiate the formation of primary ice in tropospheric clouds. It is fairly well understood that in mixed phase clouds precipitation develops by the growth of ice crystals at the expense of the evaporating water drops in what is called the Bergeron-Findeisen process. However, the role of IN in the development of clouds and precipitation is still poorly understood and needs to be studied (Levin and Cotton, 2007).

The number concentration of IN as well as the temperature and supersaturation required to “activate” IN are considered as key information for the understanding of primary ice formation in clouds. However, the concentration of ice particles in a cloud can exceed the actual IN concentration by orders of magnitude due to ice multiplication processes. Measurements with the Continuous Flow Diffusion Chamber (CFDC) of the Colorado State University (Rogers, Demott) meanwhile have provided many IN concentration data for various atmospheric environments as well as of IN chemical composition

Now, within the collaborative Research Center 641 TROPICE, funded by the German Research Foundation, two new IN counters called FINCH (Fast Ice Nucleus CHamber, a continuous flow mixing chamber) and FRIDGE (FRankfurt Ice Deposition FreezinG Experiment, a static vacuum vapour diffusion chamber) were developed and will be presented in this seminar. These instruments were funded to operate at the HALO Aircraft (G55 Gulfstream) of the German Research Foundation. First measurements using test aerosol as well as first results from the CLACE 6 campaign at Jungfraujoch research Station at 3570 m asl will be presented.