On Nucleation Pathways and Particle Size Distribution Evolutions in Stratospheric Aircraft Exhaust Plumes with H2SO4 Enhancement
FANGQUN YU, Gan Luo, Arshad Nair, Jason Herb, Alex Wong,
The State University of New York at Albany Abstract Number: 460
Working Group: Aerosols, Clouds and Climate
AbstractTo respond to the ongoing climate crisis, the top priority is to rapidly reduce emissions of carbon dioxide and other greenhouse gases, which are the root drivers of global warming. Nevertheless, because of the challenges of cutting emissions at adequate rates and the long lifetime of greenhouse gases, it is necessary to understand the full range of options available for protecting the safety of human and natural systems. Stratospheric aerosol intervention (SAI) is proposed as a climate intervention to reduce global warming and climate change impacts. Introducing particles into the stratosphere could reflect sunlight and reduce warming, but there remain uncertainties about the roles of nucleation mechanisms, ions, impurities, and ambient conditions toward generating SAI particles optimally sized to reflect sunlight. Here, we use a kinetic ion-mediated and homogeneous nucleation model to study the formation of H
2SO
4 particles in aircraft exhaust plumes. We find that for the H
2SO
4 loading rate to produce particles of desired sizes, nucleation occurs in the nascent (t < 0.01 s), hot (T = 360–445 K), and dry (RH = 0.01–0.1%) plume and is predominantly unary. Nucleation on chemiions occurs first, followed by neutral nucleation which converts most of injected H
2SO
4 vapor to particles. Coagulation in the aging and diluting plume governs the subsequent evolution to a narrow (σ
g = 1.3) particle size distribution. Scavenging by exhaust soot is negligible but can matter for impurities or incomplete evaporation and background aerosols. This research highlights the need to consider aerosol microphysical and plume dilution processes to determine the size distribution and ultimate radiative properties of SAI particles.