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RESEARCH PRODUCT

A wind tunnel study on the drop-to-particle conversion

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Abstract An experimental study was carried out to investigate the processes which occur during drop-to-particle conversion in atmospheric clouds whose drops are evaporating. The experiment was carried out in the Mainz vertical wind tunnel and in a 4-m high fall shaft. Drops consisting of aqueous solutions of NaCl, (NH 4 ) 2 SO 4 , and salts of artificial and natural ocean water, containing various kinds of solid, water-insoluble particles such as clays, were studied. The aerosol particles produced by the evaporation of drops had diameters in the range 0.1–1 μm, 5–20 μm, 40–80 μm and 100–300 μm. The shape and fall mode of these particles are discussed. It was found that the aerosol particles formed did not break up or splinter during the evaporation of drops. This led to the conclusion that, in evaporating atmospheric clouds, each evaporating drop produces by drop-to-particle conversion one aerosol particle of mass and chemistry given by the mass and chemistry of the foreign material present in the drop.