High Potential of Asian Dust to Act as Ice Nucleating Particles in Mixed-Phase Clouds Simulated With a Global Aerosol-Climate Model

Mineral dust affects the microphysical and radiative properties of mixed-phase clouds and hence the radiative balance of the Earth by acting as ice nucleating particles (INPs). However, the importance of Asian dust as INPs is not well understood. In this study, we examined the contribution of Asian dust to global dust INPs and its effect on cloud radiative forcing (CRF) using a global aerosol-climate model with an ice nucleation parameterization that links INP number concentrations to ambient temperature and dust number concentrations. Our model well reproduces INP number concentrations measured over the Tokyo Metropolitan area in Japan during May 2017, when Asian dust was transported to Japan. Our simulation for the years 2013-2017 shows that Asian dust extends from its source regions (e.g., the Gobi and Taklimakan Deserts) to the North Pacific, North America, and the Arctic. Notably, Asian dust is transported to higher altitudes (i.e., to temperature regimes relevant for the formation of mixed-phase clouds) more efficiently than dust from other regions. The annual-mean simulated contribution of Asian dust to global dust INPs is 15%, which is 4.4 times higher than its contribution to global atmospheric dust loading (3.4%). These characteristics of Asian dust show its high potential to act as INPs in mixed-phase clouds. Sensitivity simulations show that Asian dust INPs have a positive net CRF of 0.054-0.19 W m(-2) in East Asia and the North Pacific during 2013-2017 (cf. 0.092-1.0 W m(-2) for dust from other regions).