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 obs ervations in presence of large amount of volcanic aerosols, which stro ngly 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) operate d at the same site (L'Aquila, Italy; 42-degrees-N,13-degrees-E). For e ach measurement session the relationships between the backscattering r atios at different wavelengths are fitted with an appropriate size dis tribution of the aerosols. The aerosol optical properties determined w ith this procedure allow to correct the ozone profiles. The ozone data are compared whenever possible with balloon ozonesonde measurements t aken at S.Pietro Capofiume (Italy, 45-degrees-N, 11-degrees-E) or Hohe npeissenberg (Germany, 48-degrees-N, 11-degrees-E) and they generally show a good agreement. The ozone profiles can be retrieved with an ind etermination that, within the aerosol layer, ranges between +/-15 to /-35%. A systematic intercomparison is reported with data of other sta tions to assess the reliability of the method.