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Strong dependence of cubic ice formation on droplet ammonium to sulfate ratio.

American Geophysical Union

e show that the phase of ice that crystallizes in solution droplets, under conditions relevant for the upper troposphere (UT) and tropopause region (typically >188 K), is strongly dependent on the ammonium to sulfate ratio (ASR) of the solute. Droplets of aqueous (NH4)3H(SO4)2 (ASR = 1.5) freeze dominantly to cubic ice over a range of temperatures relevant for the UT and tropopause; whereas aqueous NH4HSO4 (ASR = 1.0) droplets do not freeze dominantly to ice Ic at temperatures relevant for the UT and tropopause region. We also show that the amount of cubic ice formed in the aqueous solution droplets at temperatures below 200 K is independent of droplet size, whereas a size dependence was observed at higher temperatures. The implications of these results for the phase of ice that forms in upper tropospheric ice clouds and the potential impact on climate, water vapor, and ozone are briefly discussed. An edited version of this paper was published by AGU. Copyright 2007 American Geophysical Union.

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2016-11-07

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/33688

Murray, Benjamin J., Bertram, Allan K. 2007. Strong dependence of cubic ice formation on droplet ammonium to sulfate ratio. Geophysical Research Letters 34(16) L16810/1-L16810/5.

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Bertram, Allan K.

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