Arctic aerosols and trace gases; observations at the Zeppelin station, Svalbard.

Particles affect the Earths radiation balance by absorbing and scattering part of the radiation from the sun. Particles may also affect the climate indirectly through changes of the optical properties of clouds. Different from most so called greenhouse gases, the particles show large variations in time and space due to their shorter life times (weeks). The climate impact by aerosols may therefore be different in different regions.
The greenhouse gas carbon dioxide (CO₂) has a long life time in the atmosphere (5-200 years), which results in its effect on the climate being more global. This does not imply that the level of CO₂ is constant. To the contrary, there is a very marked annual variation that largely comes from the uptake and respiration of CO₂ by vegetation. Moreover, the climate effect by CO₂ is active through out the whole day, whereas the climate effect by the aerosols is mainly important during the illuminated period of the day/year. In the polar regions the sun shines all day long in the summer, but in the winter the sun is not visible at all.

To understand and assess the human effect on the climate, regionally as well as globally, we need an in-depth knowledge about the atmospheric aerosol and greenhouse gases.

The objective of this investigation is to study substances that affect the climate, and in this case it concerns in particular carbon dioxide and atmospheric aerosols over Spitsbergen (Svalbard). The observations aim towards:

• detecting any long-term
  trends in the carbon dioxide level, as well as any trends in the amount or composition of aerosols in the background atmosphere.
• provide a basis to study processes that control the aerosol life cycle from their formation through aging and transformation, until being removed from the atmosphere.
• provide a basis to study the processes (sources, sinks, and transport pathways) that control the level of CO₂ in the atmosphere.
• contribute to the global network of stations that perform continuous measurements of atmospheric particles and trace gases to determine their effect on the Earths radiation balance and interaction with clouds and climate.