DETERMINATION OF STRATOSPHERIC AEROSOL MICROPHYSICAL PROPERTIES FROM INDEPENDENT EXTINCTION AND BACKSCATTERING MEASUREMENTS WITH A RAMAN LIDAR

An algorithm that permits the retrieval of profiles of particle mass a nd surface-area concentrations in the stratospheric aerosol layer from independently measured aerosol (particle and Rayleigh) and molecule ( Raman or Rayleigh) backscatter signals is developed. The determination is based on simultaneously obtained particle extinction and backscatt er profiles and on relations between optical and microphysical propert ies found from Mie-scattering calculations for realistic stratospheric particle size distributions. The size distributions were measured wit h particle counters released on balloons from Laramie, Wyoming, betwee n June 1991 and April 1994. Mass and surface-area concentrations can b e retrieved with relative errors of 10-20% and 20-40%, respectively, w ith a laser wavelength of 355 nm and with errors of 20-30% and 30-60%, respectively, with a laser wavelength of 308 nm. Lidar measurements t aken within the first three years after the eruption of Mt. Pinatubo i n June 1991 are shown. Surface-area concentrations around 20 mu m(2) c m(-3) and mass concentrations of 3 to 6 mu g m(-3) were found until sp ring 1993. (C) 1995 Optical Society of America