The Leipzig-TROPOS site is located the TROPOS institute building (4 km distant from the city center) and is operated by the TROPOS. The aerosol is sampled at a height of 16 m above the ground. Highly-traffic roads touch the premises only at distances of 50 m and more. A comparison of particle number size distributions at multiple sites in Leipzig confirmed Leipzig-TROPOS as a suitable urban background location. At Leipzig-TROPOS, submicrometer particle number size distributions as well as equivalent black carbon mass concentration are determined.