Despite the importance of ice formation in determining the properties of many clouds our quantitative understanding of ice nucleation is poor. Our knowledge of the ice nucleating ability of important aerosol types such as mineral dusts, soot and various biological materials has improved in recent years, but there remain significant gaps in our knowledge. For example, at temperatures above about -15°C it is unclear which aerosol species can trigger ice nucleation (Murray et al., 2012). In this talk I will discuss our laboratory work on ice nucleation by particles immersed within supercooled water droplets. We have developed several methodologies for quantifying ice nucleation over a very wide range of temperatures as well as examining the time dependence of nucleation (Broadley et al., 2012; Murray et al., 2011; Murray et al., 2010). I will present recent results on ice nucleation by a proxy for mineral dust from arid source regions; a study of nucleation by individual minerals which make up mineral dust; and ice nucleation by soils from a temperate climate with an emphasis on the completion between ice nucleation by biological and mineral components. In addition I will present our preliminary modelling work on the global distribution of ice nucleating aerosol.
References
- Broadley, S. L., Murray, B. J., Herbert, R. J., Atkinson, J. D., Dobbie, S., Malkin, T. L., Condliffe, E., and Neve, L.: Immersion mode heterogeneous ice nucleation by an illite rich powder representative of atmospheric mineral dust, Atmos. Chem. Phys., 12, 287-307, 10.5194/acp-12-287-2012, 2012.
- Murray, B. J., Broadley, S. L., Wilson, T. W., Bull, S. J., Wills, R. H., Christenson, H. K., and Murray, E. J.: Kinetics of the homogeneous freezing of water, Physical Chemistry Chemical Physics, -, 2010.
- Murray, B. J., Broadley, S. L., Wilson, T. W., Atkinson, J. D., and Wills, R. H.: Heterogeneous freezing of water droplets containing kaolinite particles, Atmos. Chem. Phys., 11, 4191-4207, 10.5194/acp-11-4191-2011, 2011.
- Murray, B. J., O'Sullivan, D., Atkinson, J. D., and Webb, M. E.: Ice nucleation by particles immersed in supercooled cloud droplets, Chemical Society Reviews, 41, 6519-6554, 2012.
