On Tuesday October 7th, the international monitoring campaign ACCEPT (Analysis of the Composition of mixed-phase Clouds with Extended Polarization Techniques) will kick-off at the CESAR monitoring site (Cabauw Experimental Site for Atmospheric Research) near Cabauw (The Netherlands). For a period of eight weeks, scientists from several meteorological knowledge institutes from Germany and the Netherlands, led by TU Delft and the Royal Netherlands Meteorological Institute (KNMI), will monitor clouds using a very diverse collection of measuring techniques. By combining the results, the researchers want to map in detail the processes taking place inside clouds.

Extended instrumental setup

Researchers from TROPOS (Leibniz Institute for Tropospheric Research - Leipzig, Germany), the LMU (Ludwigs Maximillians Universities - Munich, Germany) and Metek (Meteorologische Messtechnik GmbH - Elmshorn, Germany) will bring additional instruments to the monitoring equipment already present at CESAR. Together, the team of scientists will be able to operate a very extensive set of state-of-the-art instruments for atmospheric measurements.
The instrumental setup will be composed of Raman lidars (radars working with laser light instead of radiowaves), cloud radars, precipitation radars,microwave radiometers, a wind profiler and a Doppler lidar, a disdrometer measuring the rain drop size distribution and radiosondes which will give information about the atmospheric conditions. There will also be a HALO camera to characterise ice crystal shapes of cirrus clouds.

The laser 'Polly' being tested

Mixed-phase clouds

In the eight weeks of the campaign, the scientists will focus on mixed-phase clouds measurements. Mixed-phase clouds are frequently observed in the atmospheric temperature range between -40 and 0 °C where cloud water droplets and ice crystals can coexist. The composition of these mixed-phase clouds, plays a crucial role in the formation of precipitation and in the cloud radiative effect. The precipitation of ice crystals through layers of super-cooled liquid water affects ice crystal growth and shape.
The combined data supplied by all the instruments deployed should give very detailed information about what goes on inside these clouds. Knowing the exact behaviour and composition is not only essential for learning more about precipitation processes, but also for learning about how much light and radiation they allow to pass through, which in turn gives vital information about how clouds influence temperature and climate.

More information

Updates on the campaign can be found on the ACCEPT blog http://atmos.weblog.tudelft.nl/category/accept-2/

Contact: Yann Dufournet, This email address is being protected from spambots. You need JavaScript enabled to view it.,">This email address is being protected from spambots. You need JavaScript enabled to view it., http://staff.tudelft.nl/Y.Dufournet/, or Lukas Pfitzenmaier, This email address is being protected from spambots. You need JavaScript enabled to view it.
Science Information Officer TU Delft Roy Meijer, 015-2781751, 06-14015008, This email address is being protected from spambots. You need JavaScript enabled to view it. More on CESAR (pdf flyer) www.cesar-observatory.nl

Flyer: http://www.cesar-observatory.nl/publications/other/flyer-climate-EN.pdf