1. Investigation of the Aerosol- Cloud relation in polluted clouds Göran Frank Dept. of Physics, Div. of Nuclear Physics Lund Institute of Technology, Lund University

2. Objective: Improved understanding of the relations between aerosol properties, cloud properties and meteorological properties in the cloud formation process. This is important for a better understanding of the: Cloud formation process Cloud optical properties Precipitation initiation and cloud life time Aerosol climate effects The cloud number size distribution is a crucial property of a cloud, and it is of great importance to improve the description of which parameters affect it, and to what extent.

3. How to reach the goals: In-cloud long term measurements at the meteorological and cloud research station at the summit of mount Brocken in Germany. Measured parameters: Aerosol (dry) number size distribution Cloud droplet and cloud interstitial particle number size distribution Relation between these distributions on single particle-drop basis Chemical composition of aerosol particles (intensive periods) (AMS) Cloud liquid water content (PVM) Cloud droplet number size distr. (for validation) (FSSP) Aerosol number size distr. (SMPS) Meteorological parameters: wind velocity, temperature, pressure, etc. Cloud base height (celiometer + manual observations) Cloude type (manual observation) In-cloud relative humidity (supersaturation) ??? (CCN-counter) Updraft velocity will be estimated from calculations using measured parameters Unique instrumentation: The Droplet Aerosol Analyser DAA

4. Droplet Aerosol Analyser (DAA) Unique instrumentation Measures: – Ambient size of cloud droplets and cloud interstitial particles – Size of dry residual particles after drying – Number of particles Unique three-parameter data-set Developed in Lund (Bengt Martinsson, et al.) Development of second generation in progress: – Improved performance for long-term measurements – Improved time resolution (from 15-20 min to 4-5 min)

5. Team: Dr. Göran Frank, team leader Prof. Bengt Martinsson Dr. Staffan Sjögren, post doc (starting 2008-07-01) PhD-student (open position) Anna Persson, Bachelor work student More diploma workers needed Collaboration with BTU Cottbus, Air Chemistry Group (situated in Berlin): Dr. Wolfgang Wieprecht Dr. Karin Acker Prof. Detlev Möller

6. Long term research goal: Improved understanding of the relations between aerosol properties, cloud properties and meteorological properties in the cloud formation process. (Same as project objective) Improved methods: Development of third generation DAA for aircraft measurements.