Atmospheric Aerosols
The sources, dynamics, composition and optical effects of the solid and liquid particles suspended in the atmosphere.
Definition
Atmospheric aerosols are the suspensions of fine solid and liquid particles in air, together with the processes that create, transform, transport and remove them.
Scope
This area covers the formation of aerosol particles by nucleation and emission, their growth, coagulation and removal, their chemical composition including secondary organic material, their size distributions, and their interaction with radiation and clouds. It spans the physical dynamics of particle populations and the resulting effects on air quality and climate.
Sub-topics
Core questions
- How do aerosol particles form and evolve in the atmosphere?
- What controls aerosol size distributions and lifetimes?
- How do aerosols affect radiation, clouds and air quality?
Key theories
- Aerosol general dynamic equation
- A population balance describing how nucleation, condensation, coagulation and deposition together shape the evolving aerosol size distribution.
- Aerosol direct and indirect radiative effects
- Aerosols scatter and absorb sunlight directly and modify cloud properties indirectly, producing a net cooling that partly offsets greenhouse warming.
Mechanisms
Aerosols are emitted directly as primary particles or formed in situ by nucleation and condensation of low-volatility vapours. Their size distribution evolves through condensational growth, coagulation of smaller particles, and removal by dry deposition and wet scavenging. Particle size and composition determine how strongly aerosols scatter and absorb radiation and how readily they act as cloud condensation nuclei, linking aerosol dynamics to both air quality and climate forcing.
Clinical relevance
Aerosols are the principal component of particulate air pollution affecting human health and visibility, and aerosol-radiation and aerosol-cloud interactions are among the largest uncertainties in climate forcing.
History
Aerosol science developed from early studies of condensation by Aitken and Wilson, advanced through cloud-chamber and instrumentation work in the twentieth century, and became central to climate science as the radiative role of particles was quantified in successive IPCC assessments.
Key figures
- John Seinfeld
- Spyros Pandis
- William Hinds
Related topics
Seminal works
- seinfeldPandis2016
- boucher2013
Frequently asked questions
- Do aerosols warm or cool the climate?
- Most aerosols cool the climate by scattering sunlight and brightening clouds, though absorbing particles such as black carbon warm; the net effect is a partial offset of greenhouse warming.