Experimentalt study on homogeneous and heterogeneous nucleation in ternary vapor mixtures

The variability of the global climate is presently receiving considerable attention since apart from the scientific importance also economic aspects are becoming increasingly relevant. Thus, the evolution of the global climate and particularly possible influences by anthropogenic activities are nowadays studied extensively. In this context, atmospheric aerosols are of great relevance. At present, however, it is still difficult to quantitatively estimate the influence of aerosols in relation to the greenhouse gases or the stratospheric ozon. The liquid or solid particles suspended in the atmosphere are significantly influencing the global radiation balance. They can act directly on radiation by absorption or scattering or indirectly by acting as cloud condensation nuclei thus influencing cloud formation and therefore leading to changes of the global albedo. In this project we plan to investigate the new aerosol particle formation in ternary vapor mixtures consisting of water, nitric acid/hydrochloric acid and ammonia. Especially nitric acid is nowadays believed to be one of the most important highly soluble trace gases in the atmosphere. Numerical model calculations have shown that such ternary vapor systems can cause new particle formation in the atmosphere. In the proposed project it would for the first time be possible to test the corresponding numerical models by quantitative laboratory experiments. For that purpose we plan to apply a specially developed laser light scattering method (Constant-Angle-Mie-Scattering- Method, CAMS) which allows non-invasive quantitative measurements of number concentration and growth kinetics of condensing droplets. Comparisons to numerical models will be performed in cooperation with Prof. M. Kulmala and his research group at the University of Helsinki. The proposed experiments could lead to a substantial progress in the description of atmospheric cloud and fog formation. Besides, the results of this project would also contribute to an improvement of the global climate models, which at present are still not sufficiently accounting for the influence of aerosols.

The variability of the global climate is presently receiving considerable attention since apart from the scientific importance also economic aspects are becoming increasingly relevant. Thus, the evolution of the global climate and particularly possible influences by anthropogenic activities are nowadays studied extensively. In this context, atmospheric aerosols are of great relevance. At present, however, it is still difficult to quantitatively estimate the influence of aerosols in relation to the greenhouse gases or the stratospheric ozon. The liquid or solid particles suspended in the atmosphere are significantly influencing the global radiation balance. They can act directly on radiation by absorption or scattering or indirectly by acting as cloud condensation nuclei thus influencing cloud formation and therefore leading to changes of the global albedo. In this project we plan to investigate the new aerosol particle formation in ternary vapor mixtures consisting of water, nitric acid/hydrochloric acid and ammonia. Especially nitric acid is nowadays believed to be one of the most important highly soluble trace gases in the atmosphere. Numerical model calculations have shown that such ternary vapor systems can cause new particle formation in the atmosphere. In the proposed project it would for the first time be possible to test the corresponding numerical models by quantitative laboratory experiments. For that purpose we plan to apply a specially developed laser light scattering method (Constant-Angle-Mie-Scattering- Method, CAMS) which allows non-invasive quantitative measurements of number concentration and growth kinetics of condensing droplets. Comparisons to numerical models will be performed in cooperation with Prof. M. Kulmala and his research group at the University of Helsinki. The proposed experiments could lead to a substantial progress in the description of atmospheric cloud and fog formation. Besides, the results of this project would also contribute to an improvement of the global climate models, which at present are still not sufficiently accounting for the influence of aerosols.