Mechanisms of the aerosol indirect effects (AIE) from ice nucleating particles (INPs) are investigated with the cloud-resolving ‘Aerosol-Cloud’ (AC) model with a hybrid bin-bulk microphysics scheme coupled with a radiation scheme in 1) continental deep convection observed during the Midlatitude Continental Convective Clouds Experiment (MC3E) over Oklahoma, and 2) supercooled stratiform clouds observed during Aerosol Properties, Processes And Influences on the Earth’s climate (APPRAISE) campaign over Larkhill, UK. In both cases, the sensitivity of cloud micro- and macro-physical, and associated radiative, properties are examined with respect to inclusion of anthropogenic INPs. In both cases, anthropogenic INPs reduce the mean sizes of cloud-droplets and ice-crystals, boosting their concentrations by 10–30%. Also, their cloud extents and optical thicknesses increase with anthropogenic INPs.