SABRE Science Questions

There remain significant uncertainties in the current understanding of the chemical, microphysical and dynamical processes that regulate stratospheric aerosol and its radiative and climate impacts. The outstanding questions include:

  1. What are the relative contributions of anthropogenic and natural sources of sulfur to stratospheric aerosol mass? How do specific sources of sulfur compounds influence the sulfur loading in the upper troposphere / lower stratosphere (UTLS)?
  2. What is the contribution of organic species to the aerosol budget in the lower stratosphere as a function of latitude and season? What is the role of organics in new particle formation in the tropical tropopause layer (TTL)?
  3. How important is monsoon activity as a pathway for transporting aerosols and aerosol precursors from continental sources to the stratosphere? What is the contribution from direct transport to the stratosphere by overshooting deep convection relative to slow diabatic ascent in the TTL?
  4. What is the composition (especially black carbon content) of pyrogenically injected stratospheric aerosol? What are the radiative properties of these particles and how do they evolve with time?
  5. What is the contribution of small and moderate volcanic eruptions to stratospheric aerosol? What is the contribution from fine mode ash? What are the chemistry and microphysics of sulfate aerosol formation from volcanically injected SO2? How does this depend on the location, season and magnitude of the injection?
  6. How do variations in stratospheric aerosol loading, size distribution and composition affect stratospheric ozone chemistry?