Theme 1: Atmospheric new particle formation (NPF) and growth
  • What are the factors controlling the frequency and strength of NPF in different environments?
  • How is NPF and growth tied to the emissions and atmospheric oxidation of aerosol precursors?
  • How is atmospheric NPF and growth changing in character as a result of changing atmospheric composition and climate?
Theme 2: Cloud condensation nuclei (CCN)
  • How efficiently does atmospheric NPF produce new CCN in different environments?
  • How are CCN concentrations affected by primary emissions and atmospheric aging of primary particles?
  • How are atmospheric CCN concentrations tied with the particle number size distribution and size-resolved chemical composition?
Theme 3: Aerosol surfaces
  • How are surface-active chemical compounds, and their mixtures with other compounds in aerosol particles, partitioned between the particle surface and bulk of the particle and how does this affect aerosol water uptake and CCN activity?
  • How do surfactants affect surface tension and other particle properties relevant to gas-particle partitioning and cloud droplet activation?
Theme 4: Aerosol-cloud-radiation interactions
  • How do atmospheric NPF, secondary organic aerosol formation associated with biogenic emissions and anthropogenic pollution affect climatically-relevant cloud properties, and how do these effects interact?
  • How do aerosol-cloud interactions influence radiative transfer in the atmosphere, and what are the consequent effects on radiative forcing and ecosystem functioning?
Theme 5: Feedbacks
  • What are the main climate feedback mechanisms associated with natural emissions of aerosol precursors, and how is their strength connected with the ongoing change in climate and atmospheric composition?
  • How are air quality, climate and weather connected with each other in polluted environments?
Theme 6: Parameterizations and proxies
  • How can we improve parameterization of aerosol sources and atmospheric processes involving both aerosols and clouds, and how to implement them in a cost-effective way in large-scale modelling frameworks?
  • What are the consequences of aerosol concentrations, NPF and associated feedback mechanisms in larger spatial and temporal scales extended with the aid of proxy variables and parameterizations?