Particle size amplification of black carbon by scattering measurement due to morphology diversity


 Black carbon (BC) is an important aerosol species due to its strong heating to the atmosphere accompanied by cooling to the Earth’s surface, but its radiative forcing is poorly constrained by different regional size distributions because of uncertain reproductions of a morphologically simplified model. Here, we quantify BC morphological effect on measuring particle size using an aggregate model. We show that size distributions of loose BC particles could account for up to 45% underestimated by morphological simplification, leading to up to 25% differences by relying on the simplified model in estimating radiative forcing. We find that BC particle size is remarkably amplified for those looser and larger BC aggregates by angular scattering observations. We suggest that BC morphological diversity can be neglected in forward scattering angles (<30°), which is a useful supplement to reduce the uncertainty of radiative forcing assessment.