Atmospheric New Particle Formation Dynamics

Atmospheric new particle formation (NPF) refers to the process by which trace vapours in the atmosphere cluster together to form stable nanometre-scale particles, which can then grow to sizes capable of acting as cloud condensation nuclei (CCN). This multi-step phenomenon begins with the nucleation of molecular clusters, often involving sulphuric acid, ammonia, low-volatility organic compounds and, in some regions, iodine or nitric acid derivatives. Once initial clusters reach a critical size, they undergo growth through vapour condensation and coagulation, competing with loss processes such as scavenging by pre-existing particles. The rate and efficiency of new particle formation are strongly influenced by ambient temperature, relative humidity, precursor vapour concentrations and the existing aerosol surface area (the condensation sink). Regionally distinct mechanisms have been identified—from biogenic volatile organic compound (BVOC) oxidation driving particle growth in forested regions to acid–base stabilisation in colder urban or upper-tropospheric environments. The resulting particles contribute a significant fraction of global CCN, influencing cloud properties, radiative balance and regional climate. Advances in field measurements, chamber experiments and global modelling now allow more comprehensive representations of 11 distinct NPF pathways in climate simulations, revealing substantial spatial and seasonal variability. A deeper understanding of NPF dynamics is essential for improving air-quality management, predicting weather and climate feedbacks, and assessing the impact of anthropogenic and biogenic emissions on Earth’s radiative budget.

Research from Nature Portfolio

Recent studies have shown that the dominant mechanisms of new particle formation vary markedly across the globe and with altitude. Global simulations incorporating molecular-level experiments now represent multiple pathways, including amine- and organic-driven nucleation in polluted continental boundary layers, iodine oxide clustering over oceans and acid–base stabilisation in the free troposphere. These comprehensive models indicate that NPF contributes between 10 % and 80 % of nuclei for cloud formation at typical supersaturations, highlighting its critical role in regional climate forcing. Complementary chamber experiments under atmospheric conditions have revealed that nitric acid and ammonia can condense onto freshly nucleated clusters at temperatures below +5 °C, and at colder conditions (below −15 °C) can nucleate directly to form ammonium nitrate particles. The high vapour concentrations of nitric acid and ammonia lead to exceptionally rapid growth rates—exceeding 100 nm h⁻¹—thereby enhancing the survival of nascent particles through their most vulnerable size range and substantially increasing their likelihood of becoming CCN.

Atmospheric New Particle Formation Dynamics publication trend

The graph below shows the total number of articles in atmospheric new particle formation dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

New particle formation (NPF): The process by which gas-phase molecules nucleate to form stable molecular clusters that can grow into aerosol particles.

Nucleation rate: The number of new clusters formed per unit volume and time, often expressed in cm⁻³ s⁻¹.

Condensation sink: A measure of the rate at which vapours are removed by deposition onto existing aerosol surfaces, inhibiting nucleation.

Cloud condensation nuclei (CCN): Aerosol particles large enough to activate into cloud droplets at a given supersaturation.

Highly oxygenated organic molecules (HOMs): Low-volatility oxidation products of volatile organic compounds that contribute to particle growth.

References

1. Global variability in atmospheric new particle formation mechanisms. Nature (2024).
2. Atmospheric new particle formation and growth: review of field observations. Environmental Research Letters (2018).
3. Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors. Science Advances (2018).
4. Rapid growth of new atmospheric particles by nitric acid and ammonia condensation. Nature (2020).