Heterogeneous ice nucleation ability of NaCl and sea salt aerosol particles at cirrus temperatures

R Wagner, J Kaufmann, O Möhler, H Saathoff, M Schnaiter, T Leisner
Poster

We have investigated the heterogeneous ice nucleation ability of sodium chloride (NaCl) and sea salt aerosol (SSA) particles at cirrus cloud temperatures between 235 and 200 K in the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) aerosol and cloud chamber. Effloresced NaCl aerosol particles were found to act as INPs (ice nucleating particles) in the deposition nucleation mode at temperatures below about 225 K, with freezing onsets in terms of the ice saturation ratio, Sice, between 1.3 and 1.4 for temperatures between 220 and 200 K. Above 225 K, the crystalline NaCl particles deliquesced and nucleated ice homogeneously. Partially effloresced SSA particles were found to act as INPs in the immersion freezing mode at temperatures below about 220 K, with freezing onsets in terms of Sice between 1.25 and 1.35 for temperatures between 215 and 200 K. Above 220 K, the SSA particles fully deliquesced and nucleated ice homogeneously.

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