Cloud Microphysics and Climate Interactions

Cloud microphysics examines the formation, growth and phase transitions of cloud particles—both liquid droplets and ice crystals—and their interactions with atmospheric aerosols. Tiny aerosol particles, acting as cloud condensation nuclei (CCN) or ice nucleating particles (INP), determine cloud droplet number, size distribution and the onset of glaciation. These microphysical properties influence cloud reflectivity, lifetime and precipitation efficiency, thereby modulating the Earth’s radiative balance and hydrological cycle. Natural aerosols such as mineral dust, sea salt and biological fragments, together with anthropogenic emissions of soot and sulphate, alter CCN and INP populations, leading to regional and global changes in cloud albedo and rainfall patterns. In cold clouds, deposition nucleation and immersion freezing processes govern the transition from supercooled water to ice, affecting cloud-top temperatures and dynamics. Feedbacks arise as changes in cloud properties influence atmospheric circulation and surface temperatures, which in turn modify aerosol sources and cloud formation. Understanding these interlinked processes is crucial for improving climate projections, informing weather modification strategies and assessing the climatic impact of emissions and land‐use changes.

Research from Nature Portfolio

Recent studies have identified that primary biological aerosol particles in the Arctic peak during summer months and correlate strongly with high‐temperature ice nucleating particles. Observations at a mountain site revealed that over 90% of INP active above –15 °C are proteinaceous, implicating terrestrial biosphere emissions as a key source of ice nuclei. This work refines characterisation of biological ice nucleators and highlights their influence on regional cloud glaciation and climate feedbacks in high‐latitude environments.

Research from all publishers

Foundational reviews have synthesised the role of atmospheric bioaerosols in climate, outlining how bacteria, fungal spores and pollen function as CCN and INP and emphasising gaps in quantifying emission rates, optical properties and transport processes. Laboratory experiments have mapped heterogeneous ice nucleation onset conditions for mineral dust, soot, organic coatings and biological particles, introducing the concept of ice nucleation active surface site density to normalise activity across particle types and demonstrating that coatings often suppress ice formation. Building on these insights, combined chamber and field measurements have led to empirical parameterisations for immersion freezing by desert dust, incorporating calibration factors that reconcile instrument‐specific biases and enabling implementation in regional and global climate models.

Cloud Microphysics and Climate Interactions publication trend

The graph below shows the total number of articles in cloud microphysics and climate interactions across all publications each year (not limited to Nature Index journals).

Technical terms

Cloud condensation nuclei (CCN): Fine aerosol particles that serve as seeds for water droplet formation in clouds.

Ice nucleating particles (INP): Aerosols that trigger ice crystal formation in supercooled cloud droplets under sub‐zero conditions.

Immersion freezing: A microphysical process whereby ice forms within a supercooled water droplet containing an insoluble particle.

Deposition nucleation: Direct transition of water vapour to ice on aerosol surfaces without passing through the liquid phase.

Primary biological aerosol particles (PBAP): Biological materials emitted directly from terrestrial sources, including bacteria, fungal spores and pollen, that act as cloud‐forming nuclei.

References

1. Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic. Nature Communications (2023).
2. Primary biological aerosol particles in the atmosphere: a review. Tellus B (2012).
3. Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments. Atmospheric Chemistry and Physics (2012).
4. Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles. Atmospheric Chemistry and Physics (2015).