First coordinated measurements over Athens to study the impact of aerosols on PBL cloud formation (HygrA-CD campaign).

Under continental and Etesians wind flow he PBL height was quite deep (~ 2–2.5 km), while under Saharan wind flow conditions, the PBL height remained quite shallow (< 1–1.2 km).

The origin of the atmospheric air masses, the prevailing meteorological conditions and aerosol hygroscopicity play a major role on the cloud formation at the vicinity of the PBL.

Upward aerosol fluxes determine the number of the activated CCN at the cloud base.