Stratospheric Aerosol layer responses to volcanic and wildfire perturbations

The stratospheric aerosol layer plays a critical role in the climate system and is often disrupted by natural phenomena such as volcanic eruptions and extreme wildfire events. These perturbations differ significantly in their injection magnitude, aerosol mass, composition, and the altitude of material deposition. When coupled with the dynamic and chemical state of the stratosphere, these factors produce varied responses in the aerosol layer’s optical and microphysical properties.Quantifying microphysical responses in detail requires reliable in situ observations, such as those provided by the NOAA Balloon Baseline Stratospheric Aerosol Profiles (B2SAP) network. Spanning latitudes from 72°N to 90°S and capturing data from the surface to approximately 28 km, regular B2SAP soundings monitor the stratospheric aerosol background and the evolution of perturbations over time and space. The Portable Optical Particle Spectrometer (POPS) in the B2SAP payload measures aerosol number and  size distribution, variables crucial for understanding stratospheric aerosol microphysics and refining satellite retrievals of aerosol extinction and effective radius.In this study, we leverage data collected by B2SAP since its inception in 2019, encompassing a range of perturbations from moderate to large volcanic eruptions and extreme wildfire events, including the 2019–2020 Australian wildfires. We compare in situ observations to satellite-derived measurements, examining differences in aerosol extinction and effective radius. Additionally, we interpret POPS size distribution data alongside NASA GEOS Chemistry Climate Model outputs, providing insights into the processes driving the observed variability in stratospheric aerosol responses.