Lidar measurements of tropospheric water vapor and aerosol profiles over southeastern Italy

A combined Rayleigh-Raman lidar based on a XeF excimer laser (351 nm) has been used for the regular monitoring of tropospheric aerosols and water vapor profiles over southern Italy (40degrees20'N, 18degrees6'E) in the framework of the European Aerosol Research Lidar Network. Coincident measurements of vertical profiles of the aerosol backscattering ratio R(z), the aerosol extinction coefficient alpha(lambdao)(aer)(z), and the water vapor mixing ratio w(z) have been performed during several months to investigate the correlation of R(z) and a(lambdao)(aer)(z) with water vapor and to characterize the aerosol optical properties. A strong correlation has been found between the spatial and temporal evolution of R(z) and w(z) both in summer and in autumn regime. The experimental results have revealed that R (z) increases with w(z) and that the aerosol and water vapor burdens are lower in autumn than in the summer. The analysis of the data by using the 4-day analytical backward trajectories has revealed that the dependence of a(lambdao)(aer)(z) and R(z) on w(z) is quite affected by the typical advection patterns over the lidar site. Aerosols providing a larger contribution to backscattering ratio and extinction coefficient as w(z) increases have been monitored when air masses from northern and eastern European countries were advected over Lecce. The findings in terms of the lidar ratio S have revealed that aerosols with average S values ranging from 50 to 63 sr have been monitored when air masses from northern and eastern Europe were advected over Lecce. On the contrary, average S values ranging from 48 to 74 have been retrieved for air masses advected from North Africa.