Cézeaux-Aulnat-Opme-Puy De Dôme: a multi-site for the long-term survey of the tropospheric composition and climate change
Authors: Baray Jean-Luc , Deguillaume Laurent , Colomb Aurélie , Sellegri Karine , Freney Evelyn , Rose Clémence , Van Baelen Joël , Pichon Jean-Marc , Picard David , Fréville Patrick , Bouvier Laëtitia , Ribeiro Mickaël , Amato Pierre , Banson Sandra , Bianco Angelica , Borbon Agnès , Bourcier Lauréline , Bras Yannick , Brigante Marcello , Cacault Philippe , Chauvigné Aurélien , Charbouillot Tiffany , Chaumerliac Nadine , Delort Anne-Marie , Delmotte Marc , Dupuy Régis , Farah Antoine , Febvre Guy , Flossmann Andrea , Gourbeyre Christophe , Hervier Claude , Hervo Maxime , Huret Nathalie , Joly Muriel , Kazan Victor , Lopez Morgan , Mailhot Gilles , Marinoni Angela , Masson Olivier , Montoux Nadège , Parazols Marius , Peyrin Frédéric , Pointin Yves , Ramonet Michel , Rocco Manon , Sancelme Martine , Sauvage Stéphane , Schmidt Martina , Tison Emmanuel , Vaïtilingom Mickaël , Villani Paolo , Wang Miao , Yver-Kwok Camille , Laj Paolo 
Published: June 2020

Abstract. For the last 25 years, CO-PDD (Cézeaux-Aulnat-Opme-puy de Dôme) has evolved to become a full instrumented platform for atmospheric research. It has received
credentials as a national observing platform in France and is internationally recognized as a global station in the GAW (Global Atmosphere Watch) network.
It is a reference site of European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS
(Integrated Carbon Observing System). The site located on top of the puy de Dôme mountain (1465 m a.s.l.) is completed by additional sites located
at lower altitudes and adding the vertical dimension to the atmospheric
observations: Opme (660 m a.s.l.), Cézeaux (410 m), and Aulnat (330 m). The integration of different sites offers a unique combination of in situ and remote sensing measurements capturing and documenting the variability of
particulate and gaseous atmospheric composition, but also the optical,
biochemical, and physical properties of aerosol particles, clouds, and precipitations. Given its location far away from any major emission sources,
its altitude, and the mountain orography, the puy de Dôme station is ideally located to sample different air masses in the boundary layer or in
the free troposphere depending on time of day and seasons. It is also an
ideal place to study cloud properties with frequent presence of clouds at
the top in fall and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment,
scientific studies at the puy de Dôme strongly contribute to improving knowledge in atmospheric sciences, including the characterization of trends and variability, the understanding of complex and interconnected processes
(microphysical, chemical, biological, chemical and dynamical), and the provision of reference information for climate/chemistry models. In this
context, CO-PDD is a pilot site to conduct instrumental development inside
its wind tunnel for testing liquid and ice cloud probes in natural conditions, or in situ systems to collect aerosol and cloud. This paper reviews 25 years
(1995–2020) of atmospheric observation at the station and related scientific research contributing to atmospheric and climate science.