Aerosol Perturbations in the Upper Troposphere and Lower Stratosphere due to Volcanic and Wildfire Injections: Insights from the DCOTSS Airborne Mission

YAOWEI LI, John Dykema, Corey Pedersen, Jean-Paul Vernier, Michael Fromm, David Peterson, Xiaoli Shen, Nicole June, Amit Pandit, Jeffrey R. Pierce, Daniel Cziczo, Frank Keutsch, Harvard University

     Abstract Number: 352
     Working Group: Aerosols Spanning Spatial Scales: Measurement Networks to Models and Satellites

Abstract
Aerosols in the upper troposphere and lower stratosphere (UT/LS, altitudes of approximately 7-18 km) modulate global radiative balance by scattering and absorbing radiation, as well as affecting the nucleation of ice clouds. Additionally, aerosols in the LS affect the protective ozone layer by providing heterogeneous surfaces for halogen activation reactions and N2O5 hydrolysis. The climate and chemical impacts of UTLS aerosols depend largely on their microphysical and chemical properties, which can be significantly altered by episodic events such as volcanic eruptions and large-scale wildfires.

The NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) airborne mission, conducted in 2021 and 2022 over North America, provided an opportunity for in-situ microphysical and chemical characterization of UTLS aerosols. With the NASA ER-2 high-altitude aircraft platform, particles were isokinetically sampled up to 22 km and aerosol size distributions (130-3000 nm) were measured by an optical particle spectrometer (DCOTSS Portable Optical Particle Spectrometer, DPOPS). Aerosol chemical composition were measured using the particle analysis by laser mass spectrometry-next generation (PALMS-NG) instrument. This dataset is valuable for characterizing background UTLS aerosols, as well as perturbations from volcanic and wildfire injections. Volcanic plumes from La Soufrière eruptions in April 2021 were sampled repeatedly in the stratosphere, enabling detailed analysis of their spatiotemporal evolutions and impacts on radiative forcing and ozone depletion. A few ER-2 encounters of wildfire smoke from pyrocumulonimbus (pyroCb) events occurred in the UT. Evolution of these smoke aerosols in the UT and their radiative impacts were investigated using an aerosol microphysical model and radiative transfer calculations.