Optical Properties and Light Scattering of Atmospheric Aerosols

Atmospheric aerosols—suspensions of fine solid or liquid particles in the air—exert a profound influence on Earth’s climate, air quality and visibility through their interactions with solar and terrestrial radiation. The manner in which aerosols absorb, scatter and polarise light is governed primarily by their size distribution, chemical composition, morphology and internal mixing state. Small particles comparable in size to the wavelength of visible light give rise to distinctive angular scattering patterns, encapsulated in the phase function, while larger or heterogeneous particles generate complex multiple‐scattering effects. Key optical parameters such as the single-scattering albedo, asymmetry parameter and absorption and scattering coefficients determine the net radiative forcing of aerosol layers, influence retrieval algorithms in remote sensing and underlie in situ measurement techniques. Advances in laboratory characterisation—from polar nephelometry to angle-resolved depolarisation studies—and in numerical methods, including Mie theory, T-matrix and discrete‐dipole approximations, have enriched our understanding of how natural (e.g. mineral dust, sea salt) and anthropogenic (e.g. black carbon, organic aerosols) components modulate light propagation in the atmosphere. These insights inform global climate models and satellite retrieval schemes, enabling more accurate projections of aerosol–radiation and aerosol–cloud interactions, and yield practical benefits for air-quality management and public health assessments.

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Optical Properties and Light Scattering of Atmospheric Aerosols publication trend

The graph below shows the total number of articles in optical properties and light scattering of atmospheric aerosols across all publications each year (not limited to Nature Index journals).

Technical terms

Phase function: Angular distribution of light intensity scattered by a particle, fundamental to radiative transfer.

Single-scattering albedo: Ratio of scattering efficiency to total extinction (scattering plus absorption), indicating a particle’s relative proclivity to scatter light.

Asymmetry parameter: Mean cosine of the scattering angle, quantifying the preferential forward or backward scattering by particles.

Ångström exponent: Wavelength dependence of aerosol optical depth, used to infer particle size distribution from spectral measurements.

Depolarisation ratio: Fraction of scattered light whose polarisation state differs from that of the incident beam, sensitive to particle shape and structure.

Refractive index: Complex quantity describing how light speed and attenuation within a particle vary with wavelength and composition.

References

1. MieAI: a neural network for calculating optical properties of internally mixed aerosol in atmospheric models. npj Climate and Atmospheric Science (2024).
2. Retrievals of aerosol optical and microphysical properties from Imaging Polar Nephelometer scattering measurements. Atmospheric Measurement Techniques (2017).
3. MOPSMAP v1.0: a versatile tool for the modeling of aerosol optical properties. Geoscientific Model Development (2018).