Study of a multy-layered structure of aerosol vertical distribution over Naples performed during EARLINET project.

We have realized systematic Lidar observations of tropospheric aerosol optical properties in the urban area of Naples (40°50'N - 14°10'E, 118m a.s.l.). Aerosol backscattering and extinction profiles have been obtained at laser wavelength of 351nm and from simultaneously measurements of elastic and N2 Raman signals [1,2,3]. The measurements have been performed systematically three times for week, in the course of the EARLINET project [4], from May 2000 to December 2002. Particular care was dedicated to experimental setup and algorithms validation during the project[5]. Long time series of continuous measurements has been also carried out in order to study the evolution of the Planetary Boundary Layer (PBL) and the dynamic of the atmospheric layers. The measurements, performed from about 08:00 to 20:00 UT, allowed us to analyse the vertical aerosol distribution over the city of Naples and to link up it to local circulation phenomena observed typically in conjunction with the diurnal heating of the land and sea surfaces and during the PBL evolution. In particular, we have analyzed data showing the presence of a dual layer structure typically located in the range between 1000 and 4000 meters and with variable thickness. We have studied the optical properties of the observed layering and in some case we have analyzed its evolution over a day.