Pre-Activation of Ice Nucleating Particles in Deposition Nucleation Mode: Evidence From Measurement Using a Static Vacuum Water Vapor Diffusion Chamber in Xinjiang, China

Pre-activation of ice nucleating particles (INPs) is a potential mechanism to enhance ice generation in mixed-phase clouds, but evidence of INP pre-activation is still limited. In this study, the pre-activation of INPs in deposition mode is investigated using refreezing experiments in a static vacuum water vapor diffusion chamber with aerosols sampled in Xinjiang, China. The results indicate that the activation efficiency of INP was enhanced after pre-activation. Statistically, the INP concentration increased by 266%, 112%, and 70% at −10°C, −14°C, and −17°C after pre-activation, and more than half of the samples showed an increase in INP concentration. The increase in INP concentration has a positive correlation with the primary INP concentration before pre-activation. The analyses provide new evidence that the pre-activated INPs can act as better nuclei at temperature as warm as −10°C, and highlight the importance to find a way to consider this mechanism in models.