The CNR-IMAA Atmospheric Observatory (CIAO) is located in Potenza at the IMAA (Istituto di Metodologie per l’Analisi Ambientale), an Institute of the Italian National Research Council (CNR), a public organization of great relevance in the field of scientific and technological research. CIAO is located in Southern Italy on the Apennine mountains (40.60N, 15.72E, 760 m a.s.l.), less than 150 km from the West, South and East coasts. The site is in a plain surrounded by low mountains (<1100 m a.s.l.) and this location offers an optimal opportunity to study different kinds of weather and climate regimes.CIAO provides quality-controlled data on the vertical profiles of clouds, humidity, temperature and aerosols. CIAO observation strategy is mainly organized in order to provide quality assured measurements for satellite validation and model evaluation and to fully exploit the synergy and integration of the active and passive sensors for the improvement of atmospheric profiling.