Characterization of aerosol properties during a huge transatlantic smoke transport event using Aeolus observations in synergy with multi-platform data

Abstract

During the wildfire season on the West Coast of the US in September 2020, biomass burning smoke aerosols were continually generated, resulting in several transatlantic transport events. As a high spectral resolution lidar (HSRL), ALADIN could directly retrieve the aerosol extinction and backscatter coefficient. Targeting a large-scale tropospheric smoke transport event originating from the western US on 14 September and arriving over Europe on 21 September, a method for constructing an Aeolus smoke dataset was developed based on ALADIN observations, in synergy with multi-source data. Utilizing selected cross-sections from this dataset, the vertical structure of the smoke layers at different transport stages are presented. HYSPLIT simulations illustrate the general transport pathway connecting these layers. Statistical analyses of the complete Aeolus smoke dataset from 14 to 21 September reveal the evolution of the smoke plume throughout its transatlantic pathway. The dense smoke plume throughout the transport was characterized by mean extinction coefficients of approximately 200 Mm −1 across all selected cross-sections and a decline in AOD from 0.54 to 0.33 along the transport pathway. The smoke layers ascended from approximately 4.4 km above the US to over 6 km above the Europe and were observed above clouds upon reaching Europe. The initially decreasing and then increasing lidar ratios are likely associated with the aging process and the hygroscopic growth of smoke particles, individually. Plume separation was observed over the mid-Atlantic, and the two resulting branches were investigated individually. To our knowledge, this paper presents the first use of ALADIN for observations and analyses of a large-scale transatlantic tropospheric smoke transport. The comprehensive characterization presented herein provides valuable information for advancing global aerosol research.