**Classification of Clouds Sampled at the Puy de Dôme Station (France) Based on Chemical Measurements and Air Mass History Matrices**

**Pascal Renard 1,\* , Angelica Bianco 1,**† **, Jean-Luc Baray 1,2, Maxime Bridoux <sup>3</sup> , Anne-Marie Delort <sup>4</sup> and Laurent Deguillaume 1,2,\***


Received: 12 June 2020; Accepted: 7 July 2020; Published: 10 July 2020

**Abstract:** A statistical analysis of 295 cloud samples collected at the Puy de Dôme station in France (PUY), covering the period 2001–2018, was conducted using principal component analysis (PCA), agglomerative hierarchical clustering (AHC), and partial least squares (PLS) regression. Our model classified the cloud water samples on the basis of their chemical concentrations and of the dynamical history of their air masses estimated with back-trajectory calculations. The statistical analysis split our dataset into two sets, i.e., the first set characterized by westerly air masses and marine characteristics, with high concentrations of sea salts and the second set having air masses originating from the northeastern sector and the "continental" zone, with high concentrations of potentially anthropogenic ions. It appears from our dataset that the influence of cloud microphysics remains minor at PUY as compared with the impact of the air mass history, i.e., physicochemical processes, such as multiphase reactivity.

**Keywords:** Puy de Dôme station (PUY); cloud chemistry and physics; air mass history; oceanic vs. continental influences; partial least squares (PLS) regression
