Ferdinando De Tomasi, Maria Rita Perrone and Anna Maria Tafuro

Istituo Nazionale di Fisica della Materia, Dipartimento di Fisica, Università di Lecce, LECCE (Italy)

The Sahara region is one of the most important sources of aerosols on the world wide scale. During sand storms, dust is raised by convective motion until the upper troposphere, from which it can be effectively transported to the Mediterranean basin and Europe. We report in this paper one year of observations of Sahara dust outbreaks monitored in Lecce (40°20’ N, 18°6’ E) between May, 2000, and April, 2001. This activity has been performed as part of the European Project Earlinet. The lidar site is located on a rather flat, rural area that is at about 15 and 25 km from the Adriatic and Ionic Sea, respectively, and at about 800 km from the northern Africa coasts; because of this, it is well suited for observations of Saharan dust outbreaks that will be not contaminated by horographic effects and urban or industrial aerosols. The lidar system can detect elastic, N2 Raman and H2O Raman backscattered signals. From the combination of these signals, it is possible to measure the vertical profiles of the aerosol backscatter and extinction coefficient, the lidar ratio and the water vapour mixing ratio. Furthermore, using temperature measurements from radiosounding, it is possible to get vertical profiles of the relative humidity.

We analyze the lidar measurements from a statistical point of view. Scatter plots of the extinction and backscatter coefficient, and lidar ratio as a function of the relative humidity will be presented and the results will be compared with the models available in literature. Results on the spatial and temporal evolution of the integrated backscatter coefficient and optical thickness will be also reported. Our observations will also be supported by the satellite observations of SeaWIFS and the TOMS aerosol index data.