Environmental & Climate Sciences Department Seminar

Ship tracks are well known natural experiments of aerosol-cloud interactions. More recently, we have analysed polluted cloud tracks induced by aerosols emitted from volcanoes and wildfires and various industrial sources - such as oil refineries, smelters, coal-fired power plants, and cities (Toll et al. 2019; Nature, https://doi.org/10.1038/s41586-019-1423-9). We have been able to shed light on cloud water adjustment to aerosol-induced cloud droplet number perturbations, diurnal evolution of polluted cloud tracks and meteorological dependence of aerosol impacts on clouds. Work-in-progress shows that anthropogenic aerosols can lead both to increases and decreases in cloud fraction. While increases in cloud fraction are caused by relatively well understood aerosol-induced suppression of precipitation, decreases are induced by anthropogenic ice nuclei leading to glaciation of supercooled liquid- phase clouds. So far, we have relied mostly on passive remote sensing. For further advances in physical understanding of aerosol-cloud interactions, we suggest a field campaign sampling aerosol and polluted cloud plumes downwind of industrial aerosol sources.