Transmissivity measurements for atmospheric characterization

A study of the transmissivity in the spectral UV range for two sites (Napoli-Italy urban area, 41 degrees N 16 degrees E - 0 m a.s.l., and Potenza-Italy rural area, 40 degrees 3'N 15 degrees 44'E - 820 m a.s.l.), with different pollutant content, has been performed. Results obtained from measurements covering a period of five years (1994-1998) are shown and the variability of the transmissivity profile and its time evolution during a night has been correlated to the water vapor content at the lower height. The aerosol optical thickness has been retrieved from lidar measurements with an evident cloud extinction and the cloud lidar ratio has been estimated from the independent simultaneous measurements of the aerosol extinction and backscattering coefficients.