On the stratospheric aerosol budget at Northern mid-latitudes from 21 years of ground-based lidar and satellite observations

Abstract : The paper presents a new high-quality 21-year series of continuous stratospheric aerosol observations at Observa- toire de Haute-Provence (OHP, 44 ̊N, 6 ̊E) in Southern France using two powerful and well-maintained lidar sys- tems. In contrast to previous studies making use of the observations by aerosol-dedicated lidars operating within the Network for Detection of Atmospheric Composition Change (NDACC), we exploit the backscatter measure- ments from the off-line 355 nm channel of stratospheric ozone lidar (LiO3S) and low-gain 532 nm channel of stratospheric temperature lidar (LTA). The presented series of stratospheric aerosol backscatter and extinction at 532 nm, spanning from January 1994 through 2016, include on average 10-11 lidar acquisitions per month after careful quality screening. The OHP lidar observations are compared with global space-borne measurements of zonal-mean stratospheric extinction by SAGE II, GOMOS, OSIRIS and CALIOP instruments, altogether covering the time span of OHP lidar data sets. Both ground-based and satellite monthly-mean stratospheric Aerosol Optical Depth between 17 and 30 km altitude (sAOD1730km) series are in good cross-agreement with discrepancies well below the measurement errors, thereby ensuring the quality and coherency of all data sets exploited for our study. The global satellite observations are then used to identify the drivers of stratospheric aerosol variability observed locally by the OHP lidars. The 21-year aerosol series reflect two essential periods in the global volcanic activity over the past two decades. The first one, a long volcanically-quiescent period of low aerosol burden (0.002