Lidar and punctual observations for the characterization of the Saharan dust impact on PM 10 levels A.Boselli 1 , R. Caggiano 1 , A. Amodeo 1 , M. Macchiato 2,3 , L. Mona 1 , G. Pappalardo 1 , S. Sabia 1 , S. Trippetta 1 1. CNR - IMAA - Istituto di Metodologie per l’Analisi Ambientale C.da S. Loja, 85050, Tito Scalo (PZ)- Italy 2. CNISM - Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, UdR Napoli, Compl. Universitario di Monte S. Angelo - Via Cintia, 80126, Napoli - Italy 3. DSF - Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Via Cintia, 80126, Napoli – Italy We present a case study of a Saharan dust outbreak observed in Tito Scalo (Southern Italy, 40° 36’ N; 15° 44’ E, 760m a.s.l.) from 15 to 18 of May 2001. The study has been performed integrating tropospheric aerosol optical properties measured by an Elastic/Raman lidar system and daily concentrations of particulate matter (PM 10 ) measured at ground level by means of a low-volume gravimetric sampler. Lidar vertical resolved measurements allowed to characterize the dust cloud. Moreover, measurements performed during complete diurnal cycles, allowed to follow the temporal evolution of the aerosol vertical distribution. The observations point out the influence of vertical exchanges from higher to lower atmospheric levels on daily PM 10 concentrations. In particular, during the Saharan episode PM 10 and Fe concentrations increase from 17 to 55 μg m -3 and from 330 to 2227 ng m -3 , respectively. Because the Fe is a characteristic crustal element it could reveals the influence of the long-range transport of African desert dust on the PM 10 composition. This case study allows also to provide a devoted methodology for an optimal integration of PM 10 and multi-wavelength lidar measurements. 1. Introduction In recent years, Saharan dust storms were investigated for atmospheric transport and deposition processes and for their strong impact on the concentration levels and composition of atmospheric aerosol. In particular, a large amount of Saharan dust is transported over the Mediterranean Sea as satellite observation, modelling and ground–base measurements have shown (Moulin et al., 1998; Pérez et al., 2006; Mona et al., 2006). In many part of the Mediterranean, about 10 African dust episodes occur per year (Rodriguez at al. 2007). Each event lasts for about 4 days contributing to increase the PM 10 level at ground until to exceed the threshold limit established by European Directive (50 μg m -3 ). In particular, in Italy Saharan dust have been found to contribute on average to about 20 μg m -3 in a year. (Gobbi et al., 2007).