Quantifying the Effects of Aerosol Size Distribution on Variations in Single Scattering Albedo

Abstract Aerosol optical properties, closely linked to complex physicochemical processes, critically influence climate and environmental impacts. However, quantitative links between particle size and the changing of scattering and absorption remain insufficiently constrained. Using in‐situ aerosol observations in Beijing and global AERONET data, we quantified the respective influences of particle size distribution and chemical composition on variations in single scattering albedo (SSA). Observations indicate that variations in the particle size directly modulate SSA in most cases. Cross‐sensitivity experiments demonstrate that the size‐distribution term induces changes in SSA approximately eight times larger than those attributable to chemical composition term. We therefore introduce two new optical parameters: size‐normalized scattering coefficient (SSC) and scattering coefficient diameter (SCD). The SSC more effectively delineates the dominant control regime of different factors on SSA variability, while the SCD provides a quantitative bridge between aerosol optical properties and physical particle size. Applying this framework to global AERONET observations reveals regionally distinct correlations between SSA and SCD. The global mean SCD is approximately 0.53 μm, with regional averages range from 0.50 μm (Africa) to 0.56 μm (North America). These findings establish a new framework for constraining the role of particle size in aerosol scattering and absorption processes and provide guidance for improving aerosol radiative representations in future climate model simulations.