While there is little doubt regarding the significance of
anthropogenic greenhouse gases for global warming, it still remains difficult to
assess the influence of cirrus clouds on the climate system. To quantify their radiative (heating or
cooling) properties the microphysical processes that govern how ice particles
form and evolve in the atmosphere need to be understood. Current theory
describes these processes on a well established thermodynamic and kinetic
background – however, measurements of atmospheric water vapor taken by
dedicated instruments onboard of research aircraft and on meteorological
balloons challenge our understanding. In clear air, conditions are found that
should cause cloud particles to form spontaneously, and in clouds
non-equilibrium situations are observed to be much more persistent than
anticipated (Peter, Science, 2006).
Research aircraft typically
carry instrumentation that provides a comprehensive description of the
environment probed. However, these flights are expensive and data retrieval and
analysis are complex issues (Krämer, ACP, 2009).
The situation is much more relaxed for soundings with small balloons. Unfortunately for these - even when equipped with high quality water vapor sensors - in general information on particulate matter is not available limiting their use to understand and characterize cirrus clouds. This led us to complement balloon water vapor sensors by the COBALD optical backscatter sonde in order to study processes in and out of cirrus clouds. The combined payload is launched from the institute roof and within Switzerland from Payerne in cooperation with MeteoSwiss. In international colaboration soundings were performed from various locations including Biak (Indonesia), Niamey (Niger), Lindenberg (Germany), Sodankylä (Finland), Lauder (New Zealand), and from the German research vessel "Sonne".
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