Year-round stratospheric aerosol backscatter ratios calculated fromlidar measurements above Northern Norway

Abstract. In this work, the processing of a year-round stratospheric sulphate aerosol (SSA) dataset from day- and nighttime lidar measurements is presented. The SSA layer is of fundamental importance for the radiative balance of the atmosphere. The layer is found at altitudes between the tropopause and about 30 km. We use a state of the art Doppler Rayleigh-Mie-Raman lidar at the ALOMAR research station located in Northern Norway (69° N, 16° E) to observe the aerosol layer and derive microphysical properties. The lidar allows the investigation of SSA from small spatial and temporal scales to decadal variations. The aerosol backscatter ratio is derived by using a multi-wavelength approach and different scattering processes. Here we introduce a method for the extension of the dataset throughout the summer where measurements have to be performed under permanent daytime conditions. We calculate backscatter ratios from color ratios of elastic scattered light at the wavelengths 355, 532 and 1064 nm. These color ratios are corrected using an average backscatter ratio profile at 355 nm from the years 2000 to 2018. Thereby, we are able to extend the dataset from 2883 hours of nighttime data to 7273 hours of total data time between 2000 and 2018.