Interhemispheric differences in cirrus properties
from anthropogenic emissions (INCA)
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.
Coordinated by Johan Ström, Stockholm,
Provide a first set of data of the microphysical and morphological
properties of young cirrus clouds at southern and northern mid-latitudes,
in relatively clean and polluted air masses under otherwise comparable
Geographical Distribution of Previous Insitu Measurements
of Cirrus Properties
Source: A. Heymsfield (1999)
2.1.1 Atmospheric composition change
2.1.2 Stratospheric ozone depletion
2.1.3 Climate change prediction and scenarios
Brief Description of the Research Project:
Very small particles in the atmosphere, called aerosols, do influence
the earth's climate, directly by absorbing and scattering solar and terrestrial
radiation, and indirectly by modifying the formation processes and radiative
properties of clouds. Therefore additional anthropogenic emissions of gases
and aerosols either from sources at the ground or from air traffic alter
the earth's radiative budget and the amount and properties of clouds.
Especially the relation between aerosols and cirrus clouds needs further
investigations. Cirrus clouds appear at altitudes of about 7 to 11 km and
consist mainly of ice particles. The radiative properties of cirrus clouds
and the specific surface area of particles and ice crystals is of
importance for climatic and air cemistry processes. These processes
depend on numerous parameters as ambient conditions during cloud formation,
structure and amount of clouds, thickness and water content of clouds,
or the concentration, composition, and shape of the ice crystals, respectively.
The main goals of the project therefore are
The measurements using the same instrumentation and the same observation
strategy are scheduled for March / April 2000 in Punta Arenas, Chile, and
for September / October 2000 in Shannon, Ireland. Both campaigns will be
performed at comparable geographical latitude (50°S and 50°N, respectively)
and at the same season in local autumn.
to determine experimentally the differences in cirrus properties in air
masses with high and low aerosol load, respectively.
to obtain for the first time a data set describing the microphysical and
morphological properties of young cirrus clouds, in Southern and Northern
moderate latitudes, which means in mostly clean and polluted air masses.
to install a ground based LIDAR system for determining the magnitude of
cirrus clouds appearance together with their temporal and spatial variability
as well as their microphysical properties.