CIAO observatory main upgrade: building up an ACTRIS compliant aerosol in-situ laboratory

Abstract. This paper describes the aerosol in-situ laboratory at CIAO (CNR IMAA Atmospheric Observatory) in South Italy, outlining its configuration and detailing each instrument and sampling lines. The CIAO observatory has been collecting observations of atmospheric components since 2000. Initially the activities revolved around aerosol lidar, later radiosounding and cloud remote sensing observations were added over the years and made CIAO a leading atmospheric observatory in the Mediterranean region. In 2018, a significant upgrade started for enhancing the observational capability by adding aerosol in-situ instruments, with the objective to push new research boundaries for aerosol characterization and multi-instrumental synergistic approaches. Here, we describe each technical implementation step for building up an extensive aerosol in-situ laboratory compliant with ACTRIS (Aerosol Clouds and Trace gases Research InfraStructure) standard operating procedures. Starting from scratch, the long path initiated in 2018, with the design of the laboratory in terms of instruments, container organization, inlets and sampling lines optimizations, that required time and interactions with experts in the field. Reporting here all the details about the final solutions implemented at CIAO, this paper will be, for new aerosol in-situ laboratory, a practical guide for the implementation of the aerosol in-situ observational site.