Particle number concentration measurements

The integral aerosol number density (diameters larger than 10 nm) is measured using two TSI Condensation Particle Counters (CPC) A model 3010 with a lower cut size of 10 nm, and a model 3025 with a cut size of 3 nm. Data is logged at one minute intervals.

The particle number density typically shows a very marked seasonal variation. Lowest number densities are found during the dark winter months with values on the order of 100 cm-3 or less. However, in the summer it is not uncommon that the number densities well exceed 1000 cm-3. The exact source of these particles is not known.