Berlin 2012 – wissenschaftliches Programm

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UP: Fachverband Umweltphysik

UP 9: Poster session

UP 9.21: Poster

Mittwoch, 28. März 2012, 18:30–19:15, Poster F

Ice crystal growth from vapor phase - experiments in an electrodynamic balance — •Christiane Wender, Daniel Rzesanke, and Thomas Leisner — Karlsruhe Institute of Technology

Depending on the composition clouds can have a very different effect on the radiative forcing of the climate. The cloud particle microphysics is determining if shortwave sunlight is scattered back (cooling) or long wave earth radiation is trapped (warming). In this effect ice crystals in high cirrus clouds have an important role. Their shape and size defines the angle of backscattering and therefor also the amount of the cooling effect. [1]. We present an experiment which allows to observe the growth of individual ice crystals from the vapor phase within an electrodynamic levitator operating at variable supersaturation. The deposition freezing on microscopic AgI particles is observed in real time under a microscope, the mass change is detected with a Milikan balance. We present crystal growth rates and the dominant ice crystal morphology as a function of temperature and water vapor supersaturation over ice.

[1] Zhang, Y., Macke, A., & Albers, F. (1999). Effect of crystal size spectrum and crystal shape on stratiform cirrus radiative forcing. ATMOSPHERIC RESEARCH(52 (1-2)), S. 59-75.