Clouds with more but smaller droplets reflect more sunlight than clouds with few large droplets, and more aerosols therefore have a cooling effect on climate. Smaller droplets can also affect how long it takes for the droplets in clouds to become big enough to produce rain. The lifetime of the clouds and the precipitation patterns can therefore also be affected by aerosols. How aerosols affect clouds is one of the largest uncertainties in current climate models.
We collect aerosols at our measurement station an hour north of Lund and measure how many aerosols there are at different sizes (concentration). Another important part of our research is working with satellite data of clouds. We investigate if we can see any differences in the clouds from the satellites depending on how high the aerosol concentrations are on the ground. Through this we are trying to find out if the clouds reflect more sunlight when we have more aerosols in the air and if rainfall is affected by the particles.
A third part is in-cloud investigations of the cloud formation process and of the microphysics of clouds, related to varying aerosol properties (concentration, etc.), as well as varying cloud dynamics. A unique instrument, the Droplet Aerosol Analyser (DAA), has been developed at our department, and is in the most recent version suitable for long-term in-cloud studies. During June-October 2010, the instrument was used for measurements at the cloud station at Mt. Brocken in Germany.