Stratospheric aerosol particle size retrieval with OSIRIS limb scatter measurements

Limb scattered sunlight measurements made by the Optical Spectrograph and InfraRed Imaging System (OSIRIS) onboard the Odin satellite are used to retrieve vertical profiles of ozone, NO2 and aerosol extinction. The retrievals are performed through forward modelling of the atmosphere using SASKTRAN, a fully spherical, successive orders radiative transfer model developed at the University of Saskatchewan. The current aerosol extinction data product is retrieved using an assumed lognormal particle size distribution for typical background conditions. This assumption can produce a systematic error in the result for cases where the size distribution is affected by volcanic aerosol. This work explores the feasibility of retrieving particle size distribution parameters directly from the measurements through simulated case studies. We explore the possibility of using both multi-spectral extinction and coincident measurements at different scattering angles, obtained on the ascending and descending portions of the orbit, to retrieve particle size information, and find that in many cases, it is possible to retrieve at least one size distribution parameter. These results will be used to improve the current aerosol extinction retrieval, and potentially provide a comprehensive dataset of stratospheric aerosol particle size from the almost global coverage and decade of measurements obtained by OSIRIS.