Spatial variation of the aerosol concentration and deposition over the Mediterranean coastal zone J. Piazzola ⁎, G. Tedeschi, R. Blot LSEET, Southern University of Toulon-Var, France article info abstract Article history: Received 4 November 2009 Received in revised form 26 March 2010 Accepted 9 April 2010 A model for the spatial variation of aerosol concentrations and deposition along the coastal zone is of great interest for studies on air and water quality. In coastal areas, sea-spray aerosols generated at the sea surface by the interaction between wind and waves add to a continental contribution emitted from natural and/or anthropogenic sources. To include coastal effects in the model for the prediction of aerosol concentrations, Piazzola et al. (2003) developed the coastal Mediterranean aerosol model. The present paper deals with an extension of the Mediterranean coastal aerosol to a regional scale applied to the prediction of the sea surface flux deposition. This was achieved by the development of an automatic coupling process between the aerosol model and a regional meso-scale meteorological model which allows accounting for the details of the orography of the coast. The results show a non-homogeneous spatial coverage of aerosol concentrations over the northwestern Mediterranean. The simulations were then validated using aerosol size distributions recorded on board the ship “Atalante” for two kinds of meteorological conditions. Error calculations show a good performance of the coupling process since it predicts the aerosol concentration to within a maximum factor of 3 for particle radii between 0.1 to 10 μm. This process was then used to provide the spatial distribution of the particle deposition fluxes over the study area. © 2010 Elsevier B.V. All rights reserved. Keywords: Coastal aerosols Atmospheric models Deposition Fetch 1. Introduction Aerosols particles affect climate by scattering and absorbing radiation (Charlson et al., 1992), and may affect the heat budget. Among them, the particles generated at the air–sea interface by wave breaking represent a major component of the natural aerosol (Andreae, 1995). Seasalts dominate atmospheric depo- sition in maritime regions (Gustafsson and Franzen, 1996; Farrell, 1995). In coastal zones, however, sea spray aerosols punctually generated at the sea surface are added to a continental contribution issued from natural and/or anthropo- genic sources (Mulcahy et al., 2008; Callaghan et al., 2008). In particular, the Mediterranean Sea is a quite closed sea surrounded by specific microclimatologic zones. The aerosol mixture in coastal zones is strongly related to the changes in the wind direction that could be in turn accompanied by variations in meteorological parameters. To include coastal effects in the aerosol model for the prediction of aerosol concentrations, Piazzola et al. (2003) proposed the coastal Mediterranean aerosol model (MEDEX) based on an extensive series of measurements on the island of Porquerolles (off the French Mediterranean coast, located at about 5 km from the coastline). The main inputs of the coastal Mediterranean aerosol model are both the wind speed and the fetch, i.e., the water trajectory of the wind. The fetch actually represents the distance over water for which the wind has blown without any major change in both the intensity and direction. This parametric model showed good performances when comparing to aerosol distributions mea- sured in different Mediterranean sites (Bendersky et al., 2004; Piazzola and Kaloshin, 2005). However, the fate of aerosol particles in the marine atmosphere is largely unknown. Knowledge on the spatial variation of aerosol concentrations should be improved for better estimates of the radiative aerosol Atmospheric Research 97 (2010) 214–228 ⁎ Corresponding author. E-mail address: piazzola@univ-tln.fr (J. Piazzola). 0169-8095/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.atmosres.2010.04.003 Contents lists available at ScienceDirect Atmospheric Research journal homepage: www.elsevier.com/locate/atmos