Toward Rapid Balloon Experiments for Sudden Aerosol Injection in the Stratosphere (REAS) by Volcanic Eruptions and Wildfires

Stratospheric aerosols are greatly influenced by medium-to-large volcanic eruptions. Over the last few years, extreme wildfires have been identified as new sources of stratospheric particles, in the form of carbonaceous aerosols injected by pyrocumulonimbus (pyroCb) events in the upper troposphere and lower stratosphere, associated with significant impacts on climate and ozone chemistry. To assess the impact of wildfires and volcanic eruptions on stratospheric aerosol loadings in the Northern Hemisphere, the Rapid Balloon Experiments for Sudden Aerosol Injection in the Stratosphere (REAS) project has been initiated. REAS is an international initiative that aims to respond to sudden events impacting stratospheric aerosol composition. Seventeen balloons were launched from Reims, eastern France, between November 2021 and January 2022 to quantify the atmospheric content for both aerosols and trace/greenhouse gases from the ground up to stratospheric levels. The main measurements concerned trace gases (CO/CO₂ as tracers of smoke) and aerosol together with ozone using instruments such as a gas collector, optical particle counters, backscatter sondes, an aerosol sampler, an aerosol impactor, and ozonesondes. The Groupe de Spectrométrie Moléculaire et Atmosphérique (GSMA) launch facility provided unique possibilities of combining multiple measurements in one flight thanks to medium flights (corresponding to a 6 kg payload). While no major event impacted the stratosphere during the campaign, we particularly discuss the influence of the aged volcanic plume from La Soufrière volcano (Saint Vincent island) and smoke particles from series of pyroCb events that took place in North America. The burden as well as the optical and microphysical properties of the observed aerosols are quantified from these in situ observations in association with various satellite data.