[Zurück]

F. Stratmann, S. Augustin, S. Hartmann, B. G. Pummer, H. Grothe, T. Temkiv, D. Niedermeier, T. Clauss, J. Voigtländer, H. Wex:
"Ice nucleation on Biological Particles: Bacteria and Pollen";
Vortrag: CECAM workshop: The Role of Interfaces in Crystallization, Lausanne, Switzerland; 22.05.2013 - 24.05.2013.

Ice nucleation processes in atmospheric clouds influence both, the formation of precipitation (especially in mid-latitude clouds), and the radiative properties of clouds, and hence affect as well weather as climate (e.g., [1]). Ice nucleation in the atmosphere occurs through homogeneous and heterogeneous nucleation processes with the latter involving a usually insoluble particle acting as ice nucleus (IN), i.e., a nucleus on the surface of which the ice forms. 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 the most important mechanism when considering mixed phase clouds. Particles acting as IN are e.g. dust particles, but also biological particles like bacteria, pollen, and fungal spores.
At the Leipzig Aerosol Cloud Interaction Simulator (LACIS) [2, 3], we have been investigating the immersion freezing behavior of various particle types including pure and surface modified mineral dust particles (e.g. [4]) as well as biological particles such a bacteria and pollen [5, 6]. We will present results from these investigation focusing on the experimental techniques used, the results gained, and the fundamental and quantitative understanding we developed concerning the heterogeneous ice nucleation behavior of biological particles.

References

[1] Cantrell and Heymsfield, Bull. Am. Meteorol. Soc. 86 795 (2005).
[2] Stratmann et al. (2004), J. Atmos. Oceanic Technol. 21 876 (2004).
[3] Hartmann et al., Atmos. Chem. Phys. 11 1753 (2011).
[4] Niedermeier et al., Atmos. Chem. Phys. 11, 11919 (2011).
[5] Hartmann et al. (2012), Atmos. Chem. Phys. Discuss. 12 21321 (2012) (accepted for publication).
[6] Augustin et al. (2012), Atmos. Chem. Phys. Discuss. 12 32911 (2012) (under review).

http://www.cecam.org/workshop-4-838.html?presentation_id=10032