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Content archived on 2024-05-21

Interhemispheric differences in cirrus properties from anthropogenic emissions


Problems to be solved
Recent assessments on environmental impacts from changes in atmospheric composition stress the importance of natural and anthropogenic changes in aerosols, which may influence ozone depletion and climate forcing. One topic of growing concern is the expected increase in use of aviation fuel, which may have substantial effects on coverage, thickness, and frequency of occurrence of cirrus clouds. High water vapour contents in combination with low temperatures make cirrus clouds potentially very important in converting reservoir species to active chlorine in the midlatitude tropopause region. These high ice clouds also play an important role to the Earth's climate system. In fact, the IPCC-Aviation report of 1999 states that the key uncertainty, which has to be overcome in the future for better assessing the climate impact from aviation, is the knowledge of contrail and aerosol impact on cirrus cloudiness.
Scientific objectives and approach
Anthropogenic emissions predominantly occur in the Northern Hemisphere, which may result in a geographical difference in the effect by aerosols.
Therefore, the objectives of the INCA project are to:
I) Determine the difference in cirrus properties, which are of importance for climate and ozone distribution in the upper troposphere and lower stratosphere, in air masses with low and high aerosol loading.
II) Provide a first set of data of the michrophysical and morphological properties of young cirrus clouds at southern and northern mid-latitudes, in relatively clean and polluted air masses, under otherwise comparable conditions. To meet the objectives, the INCA project conducts the first measurements ever performed of cirrus and aerosol properties in the Southern Hemisphere and compares these observations with comparable measurements performed in the Northern Hemisphere. The aircraft measurements provide information about aerosol and cirrus properties in regions with high and low aerosol loading and remote from localized sources at southern and northern mid-latitudes: at equal relative latitudes, in equivalent seasons, using the same set of instrumentation, using the same observation strategy, within the same year
Expected impacts
The INCA project determines the background composition of the atmosphere in one of the cleanest and in one of the most polluted tropopause regions of the world. By contrasting these results a better insight about the influence of anthropogenic emissions on the change of atmospheric composition is achieved. Exploring new airspace in the Southern Hemisphere provides the necessary data to confirm an already present modulation of cirrus properties caused by anthropogenic emissions as well as the fix-points required to asses the impact from future changes in emission patterns.

Call for proposal

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EU contribution
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16 B,Frescati Hagvaeg 16 B
106 91 Stockholm

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Total cost
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Participants (6)