Global Modeling of Ice Nucleating Particles of Multiple Aerosol Species and Associated Cloud Radiative Effects

Abstract. A subset of aerosol species act as ice nucleating particles (INPs) in mixed-phase clouds, where they influence cloud distributions and lifetimes and thus Earth's radiative balance through aerosol-cloud interactions. However, few modeling studies have simultaneously considered multiple aerosol species as INPs, and the radiative effects associated with INPs remain poorly constrained. This study uses a global climate-aerosol model to evaluate the number concentrations, spatial distributions, and cloud radiative effects of INPs from multiple aerosol species, including dust, bioaerosols, marine organic aerosol (MOA), and black carbon. The model reproduces global INP observations more accurately when multiple INP sources are included compared to simulations that consider dust INPs alone. Dust accounts for 97 % of the global mean INP number concentration in clouds because of its large atmospheric abundance. However, bioaerosols – particularly bacteria with high ice nucleating ability at relatively warm temperatures (> −10 °C) – dominate INPs in the middle troposphere at low latitudes and in the lower troposphere at mid-latitudes in the Northern Hemisphere. MOA dominates INPs in the middle and lower troposphere at middle and high latitudes in the Southern Hemisphere, where concentrations of other INP-active aerosols are low. Incorporating observational constraints on the temperature dependence of INPs increases the global mean cloud radiative effect of total INPs from +0.071 to +0.19 W m⁻². These findings underscore the importance of including INPs from multiple aerosol species in climate models for better understanding of aerosol-cloud interactions via INPs.