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Laboratory Measurements Of Contact Freezing By Dust And Bacteria At Temperatures Of Mixed-Phase Clouds, Joseph Niehaus, John Becker, Alexander Kostinski, Will Cantrell

Department of Physics Publications

Laboratory measurements of freezing by aerosol particles in contact mode are presented. The fraction of particles catalyzing freezing is quantified for three mineral dusts and three strains of bacteria. This is the most comprehensive such dataset to date for temperatures greater than −20°C, relevant for warm, mixed-phase clouds. For Arizona Test Dust, feldspar, or rhyolitic ash, more than 10³ particles are required to initiate a freezing event at −20°C in the contact mode. At −15°C, more than 10⁵ particles are required. An ice-negative strain of Pseudomonas fluorescens is an order of magnitude more effective than the mineral dusts …