Wintertime aerosol optical properties in Lanzhou, Northwest China: Emphasis on the rapid increase of aerosol absorption under high particulate pollution

The evolution of aerosol absorption and the contribution of absorbing species under different severities of particulate pollution are poorly understood, though absorption is key in aerosol radiative forcing. To resolve the problems, aerosol absorbing properties from low to high particulate pollution were investigated by using intensive observations of aerosol optical properties in the winter of 2019–2020 in Lanzhou, Northwest China. The aerosol scattering coefficient increased linearly with increasing particulate matter