TROPOS is active in several international projects, which coordinate the investigation of the cloud condensation nuclei (CCN) in size and number worldwide. Usually these in-situ measurements are performed ground-based, but during intensive campaigns airborne measurements are possible as well. The activities aim at:

  • investigation of the activation behaviour of the ambient aerosol population in field under various boundary conditions (e.g. cap cloud (crosslink-->HCCT), trade wind cumuli (CARRIBA), clean/polluted marine (Melpitz/ACTRIS)
  • inventory on CCN number at a multitude of places worldwide
  • conclusions concerning the influence of the aerosol population on cloud formation and cloud characteristics
  • application of Köhler theory for development of consistent parameterization schemes of hygroscopic growth and activation (closure studies)
  • supply data on global CCN number for appliance in models (GASSP)  

A DMPS-system built at TROPOS (left) and the DMT-CCNC (right)

Activation measurements in the field are usually performed with a commercially available Cloud Condensation Nuclei Counter (CCN-100, DMT, Boulder, USA (CCNC), Roberts and Nenes (2005)) following the ACTRIS standard operation protocol (SOP). This instrument can be operated as a stand-alone instrument, which allows the determination of the total CCN number at a certain supersaturation or in combination with a DMA for size segregated activation scans. The later set-up allows for diameter (20-800nm) and supersaturation scans (0.07 - 1%), and thereby allow for measurements of total aerosol size distributions as well as cloud condensation nuclei distributions at a certain supersaturation.

Recent measurements/results:

  • Sketch of the typical measurement set-up.

  • During cap cloud experiment at Mount Schmücke, the influence of cloud processing on the CCN behavior was investigated. Cloud processing lead to more hygroscopic, respectively more CCN active aerosol particles.

  • First data from continuous measurements at the TROPOS field station Melpitz after they their launch in August 2012 (

  • Unique data set of CCN spectra over the Atlantic Ocean between Kapstadt and Bremerhaven and Punta Arenas and Bremerhaven from three Polarstern cruises.

  • Time series taken during the CARRIBA campaing on ground and airborne at Barbados, showing total aerosol number concentration (squares in black and green, green denoting new particle formation) and CCN number concentrations from different datasets (blue line).