Anthropogenic aerosol point sources exposed through satellite-based identification of polluted cloudsLong-term impact of industrial pollution sources on cloud properties

It is well known that aerosols can increase the number of droplets in clouds. Increased droplet numbers have been observed over oceans as ship tracks , and more recently over continents as industry tracks (Toll et al 2019 Nature https://doi.org/10.1038/s41586-019-1423-9). However, it is expected that the influence of aerosols on cloud properties is broader and exists in many more cases than those with high-contrast visible cloud tracks.

To gain a better understanding of the pollution's effect on clouds, we analyzed cloud properties around hundreds of industrial sites over a 20-year period using MODIS satellite data. We simulated aerosol dispersion using the HYSPLIT model and reanalysis winds, and compared the properties of aerosol-polluted cloud areas to the properties of nearby unpolluted clouds. Importantly, we conducted several null experiments to rule out that systematic differences between polluted and unpolluted areas arise from differences in orography or land cover, prevailing weather patterns, or other surrounding pollution sources.

Preliminary results suggest that aerosol-dispersion modelling allows to successfully identify anthropogenic aerosol point sources that lead to increased cloud droplet numbers