ICOS stands for Integrating Cloud Observations from Ground and Space - a Way to Combine Time and Space Information and is a project granted by the German Research Community (DFG).

Cloud processes remain one of the largest challenges in atmospheric research partly due to a gap in statistically significant observations of cloud macro- and microphysical properties. The most detailed and continuous observations available today come from the combination of state-of-the-art ground-based sensors at a few “super sites” world wide. In order to derive the atmospheric state from all measurement information, sophisticated retrieval techniques need to be developed. In this respect, the integrated profiling technique (IPT) has been established to provide cloud liquid water (LWC) profiles with their error and the associated environmental conditions (temperature, humidity) from a combination of microwave radiometer, cloud radar and a priori information.

Within the project ICOS, this method will be extended by incorporating satellite observations by Meteosat SEVIRI into the IPT optimal estimation framework for the additional retrieval of cloud microphysics (effective radius, optical thickness) and cloud radiation budget. In addition SEVIRI measurements will be exploited to provide auxiliary information on
a) the history of the cloud observed at the super site (life time, microphysical development, environment) and
b) the representativeness of the cloud for the cloud field around the site.
The method will be developed on the basis of existing data sets from observation sites at Cabauw, Lindenberg and AMF/Murg Valley.

1. Incorporate MSG measurements into the IPT in a physically consistent way.
2. Determine the temporal evolution (history) of the air mass which transports the cloud observed by ground-based observations as a new parameter in cloud observation.
3. Assess the spatial representativeness of ground-based column observations (upscaling).
4. Compare the cloud radiation budget from observation and radiative transfer modeling to better understand the energy-transformation of the cloudy atmosphere and its feedback in the climate system.