[Zurück]

H. Wex, P. DeMott, H. Grothe, B. G. Pummer, Y. Tobo, S. Augustin, T. Clauss, S. Hartmann, D. Niedermeier, M. Raddatz, J. Voigtländer, F. Stratmann:
"Results and implications derived from measurements of different types of ice nuclei with the Leipzig Aerosol Cloud Interaction Simulator";
Vortrag: Davos Atmosphere and Cryosphere Assembly 2013, Davos, Switzerland; 08.07.2013 - 12.07.2013; in: "Davos Atmosphere and Cryosphere Assembly DACA-13", Davos Atmosphere and Cryosphere Assembly DACA-13, 13/Davos (2013), S. 481.

Ice containing clouds permanently cover 40% of the earth's surface and have a large influence on both, weather and climate. Therefore, understanding the processes that form ice in these clouds are important. It is known that there are two main pathways of atmospheric ice formation, namely homogeneous and heterogeneous ice nucleation. The latter involves aerosol particles that act as ice nuclei (IN), and these IN can be e.g. dust particles or biological particles like bacteria, pollen and fungal spores. Different heterogeneous freezing mechanisms do exit, with their relative importance for atmospheric clouds still being debated. However, there are strong indications that immersion freezing is one of the important or maybe even the most important mechanism when considering mixed phase clouds (Murray et al., 2012). What we are still lacking is a) the fundamental process understanding on how aerosol particles induce ice nucleation and b) means to quantify ice nucleation in atmospheric models. Concerning a) there most likely is not only one answer, considering the variety of IN found in the atmosphere. With respect to b) different approaches have been suggested. However it is still being debated which would be a suitable way to parameterize laboratory data for use in atmospheric modeling. In this presentation, both topics will be addressed. Using the Leipzig Aerosol Cloud Interaction Simulator (LACIS) (Hartmann et al., 2011), we examined different types of dust particles with and without coating, and biological particles such as bacteria and pollen, with respect to their immersion freezing behavior. We will summarize our findings concerning the properties controlling the ice nucleation behavior of these particles and present means for parameterizing their respective ice nucleation behavior.
References:
Hartmann et al. (2011), Atmos. Chem. Phys., 11, 1753-1767.
Murray et al. (2012), Chem. Soc. Rev., 41, 6519-6554.

ice nucleation, bioaerosols, pollen

http://www.daca13.org/wsl/daca13/program/DACA-13_Abstract_Proceedings.pdf