Stratospheric Smoke With Unprecedentedly High Backscatter Observed by Lidars Above Southern France

Extreme pyro-convection events triggered by wildfires in northwest Canada and U.S. during August 2017 resulted in vast injection of combustion products into the stratosphere. The plumes of stratospheric smoke were observed by lidars at Observatoire de Haute-Provence (OHP) for many weeks that followed the fires as distinct aerosol layers with backscatter reaching unprecedentedly high values for a non-volcanic aerosol layer. We use space-borne CALIPSO lidar to track the spatiotemporal evolution of the smoke plumes before their detection at OHP. A remarkable agreement between ground- and spaced-based lidars sampling the same smoke plume on a particular date allowed us to extrapolate the OHP observations to a regional scale, where CALIPSO reported extreme AOD values as high as 0.21. On a monthly time scale, the lidar observations indicate that boreal summer 2017 forest fires had a hemisphere-scale impact on stratospheric aerosol load, similar to that of moderate volcanic eruptions.