Improving Aerosol Absorption Estimates Via Size‐Resolved Constraints Based on AERONET and In Situ Measurements

Abstract Accurate aerosol particle size distribution is essential for estimating radiative forcing but is often hindered by assumptions that oversimplify more physical approximations of aerosol mixing state and size. This work performs a single‐site observational‐closure study that combines AERONET multi‐wavelength extinction and absorption retrievals, in situ observations of particle size, and Mie modeling over multi‐waveband, while treating the BC‐sulfate core‐shell scheme as a mass‐ and number‐conserved, radiatively‐closed set of probabilistically possible solutions and quantifying the resulting mixing, number concentration, and radiative forcing solution space. Results show conventional retrievals overestimate coarse‐mode particles and internal mixing, leading to higher single scattering albedo and broader asymmetry coefficient. Ground‐based constraints yield more physically consistent PSDs and systematically modifies aerosol optical properties, especially for smaller particles within sub‐2.5 micron range. Radiative transfer simulations using these constrained properties reveal enhanced atmospheric heating alongside reduced top‐of‐atmosphere cooling, underscoring the sensitivity of forcing to size‐resolved multi‐waveband constraints.