Dust Glaciation Effects on Mixed-Phase Clouds with a Global Climate Model Constrained by Observations (Invited Presentation)

Mineral dust is known to be the most abundant ice nucleation particles (INP) in the atmosphere, critical for ice generation in cold clouds. While there have been many studies on the dust radiative effects by scattering and absorbing solar and terrestrial radiation, the radiative effects and climate impacts of dust on cold clouds by acting as INPs are far less quantified and largely unknown. In this study, we investigate and quantify the dust indirect effects through glaciation of mixed-phase clouds with the NCAR Community Atmosphere Model version 5 (CAM5) with a sophisticated treatment of cloud microphysics. The model representations of ice nucleation and depositional growth of ice crystals through the Wegener–Bergeron–Findeisen (WBF) process are improved and constrained by the DOE ARM ground-based as well as satellite remote sensing observations. By designing sensitivity experiments with and without dust INPs, we find that dust particles exert a global radiative warming effect of ~0.2 W m^-2 through the glaciation of mixed-phase clouds, thereby reducing the magnitude of shortwave cooling of this type of clouds. The uncertainty of this estimate with respect to ice nucleation parameterizations of dust INPs in the model is also quantified.