Advancing global aerosol classification: Source-compositional typology and variability from 30 years (1993-2024) of...

Aerosol classification is pivotal for understanding atmospheric composition, radiative forcing, and air quality; however, existing global schemes often lack detailed source and compositional specificity. This study introduces a novel global aerosol classification framework integrating source characteristics and chemical composition, utilizing three decades of AERONET Level 1.5 data from 413 stations (1993-2024). Employing Fuzzy C-Means (FCM) clustering with a simultaneous feature selection and cluster optimization process, we identified eight key aerosol parameters- single scattering albedo (SSA), absorption Ångström exponent (AAE), real and imaginary refractive indices (RIR, RII), sphericity (SP), and multi-band Ångström exponents- for robust classification. The resulting seven aerosol classes- Urban/Industrial Pollution (Sulfate), Biomass Burning (Smoky Sulfate), Biomass Burning-2 (Sulfurous Smoke), Mixed-Scattering (Sulfurous Dust 1), Mixed-Absorbing (Sulfurous Dust 2), Dust (Dust), and Polluted Marine (Marine Sulfate) demonstrate strong intra-cluster compactness and inter-cluster separation. This framework advances prior typologies by distinctly separating mixed aerosols into scattering and absorbing types and disaggregating biomass burning aerosols into two compositionally unique categories, enhancing radiative and transport characterizations. Comparative analysis confirms consistency with existing schemes while offering superior compositional detail. Decadal analysis reveals a global shift from primary to aged/mixed aerosol types, with declining industrial pollution in developed regions, rising anthropogenic influences in emerging economies, and evolving biomass burning signatures, while natural dust remains relatively stable. This classification enhances interpretability for radiative forcing assessments, climate modeling, aerosol-cloud interactions, and satellite retrievals, providing a more nuanced understanding of global aerosol dynamics.