CONTINUOUS LIDAR MEASUREMENTS OF STRATOSPHERIC AEROSOLS AND OZONE AFTER THE PINATUBO ERUPTION .1. DIAL OZONE RETRIEVAL IN PRESENCE OF STRATOSPHERIC AEROSOL LAYERS

We report stratospheric DIAL (DIfferential Absorption Lidar) ozone observations in presence of large amount of volcanic aerosols, which strongly affect the inversion of the backscattering signals. The retrieval method is based on the use of three wavelengths, two from the O3 DIAL (308 and 351nm) and a third one from an aerosol lidar (589nm) operated at the same site (L'Aquila, Italy; 42-degrees-N,13-degrees-E). For each measurement session the relationships between the backscattering ratios at different wavelengths are fitted with an appropriate size distribution of the aerosols. The aerosol optical properties determined with this procedure allow to correct the ozone profiles. The ozone data are compared whenever possible with balloon ozonesonde measurements taken at S.Pietro Capofiume (Italy, 45-degrees-N, 11-degrees-E) or Hohenpeissenberg (Germany, 48-degrees-N, 11-degrees-E) and they generally show a good agreement. The ozone profiles can be retrieved with an indetermination that, within the aerosol layer, ranges between +/-15 to +/-35%. A systematic intercomparison is reported with data of other stations to assess the reliability of the method.