Goal of the workshop

Cirrus clouds cover on the average 20-30% of the Earth, and even much more when sub-visible cirrus is included. Cirrus clouds are an important modulator of the radiative energy flow in the Earth's atmosphere, and they are able to both heat or cool the atmosphere, depending on their micro-physical and radiative properties, their geographical location and altitude, and on time. They are part of the hydrological cycle and affect the humidity field in the upper troposphere. They allow heterogeneous chemistry to occur and hence play a role in regulation of tropospheric ozone. Finally, they are part of the weather system.

So far, cirrus clouds are generally perceived as isolated objects, having certain micro-physical and radiative properties. However, they are situated in an environment that has properties allowing (1) cirrus clouds to form and (2) to persist for a while. Generally the properties of this environment have received much less attention than the embedded cirrus clouds.

There has been some research on so-called ice-supersaturated regions in the recent years. However, also these regions have been treated as isolated objects, and in all studies data sets have been cleared from cloud influences as much as possible before analysis.

Evidently, there must be a strong relatedness between cirrus clouds and their supersaturated surroundings. We strongly feel a necessity to drive cirrus research into a more system analytic direction, i.e. not only to consider cirrus on the one hand and cloud free ice-supersaturated regions on the other, both as isolated objects, but to integrate these two directions and to obtain the view of ice-supersaturated regions with embedded cirrus clouds. Research in this direction is still in its infancy, and the goal of this workshop is thus twofold:

1. to raise the awareness of the current "one-dimensional perception" of cirrus;
2. to trigger research into the new "system analytic" direction of considering supersaturated airmasses in interaction with their embedded cirrus clouds.