Alicenet – An Italian network of Automated Lidar-Ceilometers for 4D aerosol monitoring: infrastructure, data processing, and applications

Abstract. The vertically-resolved information on aerosol particles represents a key aspect in many atmospheric studies, ranging from aerosol-climate interactions to those investigating aerosol impacts on air quality and human health. This kind of information can be primarily derived by lidar active remote sensing and extended networks of these systems are currently run at the global scale. A network of Automated Lidar-Ceilometers (ALCs), Alicenet, was set up in Italy in 2015 by the Institute of Atmospheric Sciences and Climate (ISAC) of the National Research Council (CNR). Alicenet grew up in these years as a cooperative effort of Italian institutions dealing with atmospheric science and monitoring, and includes regional Environmental Protection Agencies, Universities and Research Centres. In the current configuration, the network runs both single-channel ALCs and dual channel, polarisation-sensitive systems (PLCs) operating in very different environments (urban, coastal, mountainous and volcanic areas) from Northern to Southern Italy, thus allowing the continuous monitoring of the aerosol vertical distribution across the country. Alicenet also contributes to the EUMETSAT program E-PROFILE, filling an Italian observational gap compared to other EU Member States. In this work, we present the Alicenet infrastructure and a detailed description of the specifically-developed data processing chain converting raw instrumental (Level 0) data into quantitative information on aerosol properties, with output products ranging from attenuated backscatter to aerosol mass and vertical stratification from the surface up to the upper troposphere (output data Levels 1–3). Overall, this setup provides from near real-time to long-term overviews of the 4D aerosol field over Italy. Examples of both are reported in this work. Specific comparisons of the Alicenet products to relevant independent measurements of different parameters (e.g. surface PM10, sunphotometer AOD) are also included, revealing the good performances of the Alicenet algorithms. Overall, Alicenet represents a valuable resource to extend the current aerosol observational capabilities in Italy and in the Central European Mediterranean area, and contributes to bridge a gap between atmospheric science and its application to specific sectors, among which: a) air quality, b) solar energy, c) aviation safety. More in general, the maturity of the ALC/PLC instrumentation and of the data processing tools available within the wider international scientific/technical atmospheric community suggest lidar-ceilometer networks could usefully integrate current EU Atmospheric Research Infrastructures for aerosol studies.