ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-3-5755-2003 The vertical distribution of aerosols, Saharan dust and cirrus clouds at Rome (Italy) in the year 2001 Gobbi G. P. 1 Barnaba F. 1 Istituto di Scienze dell’Atmosfera e del Clima – CNR, Roma, Italy 14 11 2003 3 6 5755 5775 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/3/5755/2003/acpd-3-5755-2003.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/3/5755/2003/acpd-3-5755-2003.pdf

A set of 813 lidar profiles of tropospheric aerosol and cirrus clouds extinction and depolarization observed at Rome, Italy, between February 2001 and February 2002 is analyzed and discussed. The yearly record reveals a meaningful contribution of both cirrus clouds (38%) and Saharan dust (12%) to the total optical thickness (OT) of 0.26, at 532 nm. Seasonal analysis shows the planetary boundary layer (PBL) aerosols to be confined below 2 km in winter and 3.8 km in summer, with relevant OT shifting from 0.08 to 0.16, respectively. Cirrus clouds maximize in spring and autumn, in both cases with average OT similar to the PBL aerosols one. With the exception of winter months, Saharan dust is found to represent an important third layer mostly residing between PBL aerosols and cirrus clouds, with yearly average OT~0.03. Saharan dust and cirrus clouds were detected in 20% and in 45% of the observational days, respectively. Validation of the lidar OT retrievals against collocated sunphotometer observations show very good agreement. These results represent one of the few yearly records of tropospheric aerosol vertical profiles available in the literature.