Cloudnet is an infrastructure established in the frame of the research project Cloudnet supported by the European Commission under the Fifth Framework Programme.

The project, which started on 1 April 2001, aimed to use data obtained quasi-continuously for the development and implementation of cloud remote sensing synergy algorithms. The use of active instruments (lidar and radar) results in detailed vertical profiles of important cloud parameters which cannot be derived from current satellite sensing techniques.

The network was established starting from three already existing cloud remote sensing (CRS) stations (Chilbolton - UREAD, Cabauw - TUD, Sirta - CNRS and Lindenberg - DWD). In the frame of ACTRIS project, it will be extended by incorporating four new sites in Northern Europe and the Mediterranean region: Mace Head (NUIG), Potenza (CNR), Sodankyla (UHEL) and Hyytiala (UHEL). ACTRIS will also aim to establish a data centre that comprises three data centres (EARLINET, Cloudnet and the CLRTAP-EMEP database EBAS).