What are aerosol-cloud interactions?

The role of aerosols in the climate system is poorly understood. It is the goal of BACCHUS to better understand how aerosols affect clouds and climate. This will improve projections of future climate and will improve the scientific basis for developing sustainable policies for Europe.

Aerosol particles

Aerosol particles are small particles or droplets suspended in air. They are omnipresent in our atmosphere and although they are tiny they have a large impact on the properties of air and play a major role in our climate system. Aerosol particles can...

Cool our planet source: http://www.haus-und-wohnen.ch Similar as a parasol aerosol particles can reflect parts of the visible light back to the sun and therefore reduce the amount of solar energy reaching the surface of our planet.

Warm our planet source: http://climatekids.nasa.gov/ Similar as greenhouse gases, some aerosol particles can absorb and emit thermal radiation and thus enhance the natural greenhouse effect.

Interact with clouds Aerosol particles can serve as nuclei to facilitate the condensation of water vapour from the air and have a large effect on the properties of clouds. For more detailed information see below. The EU project BACCHUS analyses the interactions between aerosol particles and clouds.

Impact ozone Aerosol particles can provide surfaces for certain chemical reactions that can only occur where gases are in contact with liquids or particles and play a major role in atmospheric ozone chemistry. The EU project StratoClim analyses the role of aerosol particles at higher atmospheric levels in climate.

Harm human health Aerosol particles are an important factor in air quality and have an adverse effect on human health. The EU project DACCIWA analyses the impact of aerosol particles on air quality and climate in West Africa.

Types of aerosol

Various different kinds of aerosols exist in our atmosphere. The most prominent sources of aerosols are: Mineral dust from soils in arid regions; evaporation of sea spray, producing little sea salt particles; condensation of mostly biogenic organic compounds into various types of organic droplets; anthropogenic emissions of soot; anthropogenic and natural emissions of sulfur containing chemical species, which produce droplets of sulfuric acid in the atmosphere; and at higher atmospheric levels also: the condensation of nitric acid that forms from mostly biogenic nitrous oxide and smoke from the evaporation of meteorites.