Quantifying the Contribution of Soot and Dust to Ice Formation in Cirrus Clouds – a Model Study using a new Parameterization Framework

Aerosols, from most different sources and chemical composition, play an important role in the Earth's atmosphere. For example, they directly affect the radiative budget and essentially influence the formation and life cycles of clouds through ice nucleation processes. Hence, aerosols and their ice nucleating ability are an important input parameter for weather and climate models. During the previous years, the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber was used to extensively measure the ice nucleating properties of different aerosols under conditions relevant for the atmosphere. Numerous experiments were performed with a broad variety of aerosol types and under different freezing conditions. A reanalysis of these experiments offers the opportunity to develop a uniform parameterization framework of ice formation for many atmospherically relevant aerosols in a broad temperature and humidity range. The analysis includes both deposition ice nucleation and immersion freezing.

The aim of this study is to use the AIDA data set for developing a comprehensive parameterization for heterogeneous ice formation mainly by using the Ice Nucleation Active Surface Site (INAS-) density approach. The new parameterization is implemented into the online- coupled COSMO-ART model (Vogel et al. (2009)), which is based on the operationally used weather forecast model COSMO from the German Weather Service (DWD). The COSMO-ART model includes the physical and chemical impacts of aerosols on clouds and radiation via direct and indirect effects. In this framework, the contribution of different types of aerosols to heterogeneous ice formation can be investigated.

This contribution will show the new parameterizations for immersion freezing and deposition nucleation of soot aerosols and natural desert dust particles. First model results on the role of heterogeneous ice nucleation in cirrus formation will also be shown. The model results from case studies will be compared to in- situ measurements from the MACPEX campaign 2011 (Cziczo et al. (2011)).

Cziczo, D., Froyd, K., Hoose, C., Jensen, E., Dioa, M., Zondlo, M., Smith, J., Twohy, C. and Murphy, D. Science, 340, 1320-1324

Hoose, C. and Möhler, O. (2012) Atmos. Chem. Phys. 12, 9817-9854

Niemand, M., Möhler, O., Vogel, B., Hoose, C., Connolly, P., Klein, H., Bingemer, H., DeMott, P.J., Skrotzki, J. and Leisner, T. (2012) J. Atmos. Sci. 69, 3077-3092

Vogel, B., Vogel, H., Bäumer, D., Bangert, M., Lundgren, K., Rinke, R. and Stanelle, T. (2009) Atmos. Chem. Phys. 9, 8661-8680