How clouds are formed even at low temperatures?

Aerosol particles in the air that are invisible to the naked eye allow the formation of clouds.


There are small aerosol particles floating in the air constantly. Though, the particles are not visible to the naked eye and perform a significant role in the atmosphere by allowing the formation of clouds.

On the other hand, aerosol particles have high concentrations and thus harmful to health. Notwithstanding the ordinary aerosol sources, for example, burning procedures or atomization processes, nanoparticles can likewise shape from following gases specifically in the environment.

By using mass spectrometers, scientists at the University of Innsbruck now have quantitatively tested the initial particle growth under atmospheric conditions. Up until this point, it has been known that natural gases, for example, those discharged by vegetation – recognizable, for instance, by the characteristic smell of coniferous forests – add to the development and growth of nanoparticles after chemical reaction with ozone and OH radicals in the atmosphere.

First author Dominik Stolzenburg of the University of Vienna said, “In particular, the initial stage of particle formation plays an important role because the particles in the size range below 10 nanometers are rapidly lost by collisions with larger particles, to which the nanoparticles adhere. Only with rapid growth, the nanoparticles survive long enough to remain relevant for cloud formation processes. For this purpose, however, molecules are needed that can also condense under atmospheric conditions.”

In collaboration with Paul Winkler from the University of Vienna and Armin Hansel from the University of Innsbruck at CERN, scientists have discovered that the contribution of natural substances to development over a wide temperature run assumes a noteworthy part.

As a component of the CLOUD venture, it has been demonstrated that particularly at cold temperatures of – 25 ° C substances can gather that would be excessively unstable in warm conditions (+25 ° C) and would in this way remain gaseous. This implies even in colder regions of the earth (eg in the center troposphere, ~ 6 km) nanoparticles can be shaped from natural precursor gases, in spite of the fact that the chemical reactions take place there essentially slowed down.

The contribution of organic substances to cloud formation processes could, therefore, be higher than expected. The study is published in the journal PNAS within the framework of the CLOUD project at CERN.


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