Ice nucleation by aerosols from anthropogenic pollution

Abstract

The formation of ice particles in the atmosphere strongly affects cloud properties and the climate. While mineral dust is known to be an effective ice nucleating particle, the role of aerosols from anthropogenic pollution in ice nucleation is still under debate. Here we probe the ice nucleation ability of different aerosol types by combining 11-year observations from multiple satellites and cloud-resolving model simulations. We find that, for strong convective systems, ice particle effective radius near cloud top decreases with increasing loading of polluted continental aerosols, because the ice formation is dominated by homogeneous freezing of cloud droplets that are smaller under more polluted conditions. In contrast, an increase in ice particle effective radius with polluted continental aerosols is found for moderate convection. Our model simulations suggest that this positive correlation is explained by enhanced heterogeneous ice nucleation and prolonged ice particle growth at larger aerosol loading, indicating that polluted continental aerosols contain a significant fraction of ice nucleating particles. Similar aerosol-ice relationships are observed for dust aerosols, further corroborating the ice nucleation ability of polluted continental aerosols. By catalyzing ice formation, aerosols from anthropogenic pollution could have profound impacts on cloud lifetime and radiative effect as well as precipitation efficiency.

Distinct Impacts of Increased Aerosols on Cloud Droplet Number Concentration of Stratus/Stratocumulus and Cumulus

“…The results further support our explanation that the different w in Cu and Sc, which governs the responses of S eff to aerosols, could be the underlying cause for the distinct AIE. Previous studies on ice clouds also revealed that the convection strength and water vapor could modulate the opposite AIE (Zhao, Liou, et al, 2018;Zhao et al, 2019) but the present study focuses on warm clouds with a different underlying mechanism.…”

Understanding Hailstone Temporal Variability and Contributing Factors over the U.S. Southern Great Plains

“…We understand the uncertainties and caveats associated with using MODIS AOD data, but it is the only aerosol dataset available for such a long time period and over a large region, and it has been used for numerous observational studies in studying aerosol effects (e.g., Koren et al 2010;Peng et al 2016;Jiang et al 2018;Zhao et al 2019). Statistical significance of the correlation between AOD and hail occurrence is determined from 10 000 bootstrapped resamples.…”

“…If the partial correlations are similar to the corresponding total correlation, the meteorological parameters would have little effect on the total correlation. This technique was used to look at covariations of meteorological parameters with aerosols in a few previous studies (Zhao et al 2018(Zhao et al , 2019. The partial correlation calculations are conducted with nine meteorological parameters shown in Table 3 (top) eliminated individually and simultaneously.…”

Resolving the size of ice-nucleating particles with a balloon deployable aerosol sampler: the SHARK

“…Tobo et al (2019) recently reported that dust and biological material from glacial valleys in Svalbard may be an important source of INPs in the region. We also note that we sampled while the Oden was moored in the port of Longyearbyen where local pollution sources may have been significant (Zhao et al, 2019).…”