Substantial convection and precipitation enhancements by ultrafineaerosol particles

Abstract

Aerosol-cloud interactions remain the largest uncertainty in climate projections. Ultrafine aerosol particles smaller than 50 nanometers (UAP) can be abundant in the troposphere but are conventionally considered too small to affect cloud formation. Observational evidence and numerical simulations of deep convective clouds (DCCs) over the Amazon show that DCCs forming in a low-aerosol environment can develop very large vapor supersaturation because fast droplet coalescence reduces integrated droplet surface area and subsequent condensation. UAP from pollution plumes that are ingested into such clouds can be activated to form additional cloud droplets on which excess supersaturation condenses and forms additional cloud water and latent heating, thus intensifying convective strength. This mechanism suggests a strong anthropogenic invigoration of DCCs in previously pristine regions of the world.

Long‐Term Fog Variation and Its Impact Factors Over Polluted Regions of East China

“…In YRD and PRD (Figures b and c), before 1985, fog days increased faster in city stations than in background stations. During this slow urbanization stage, the faster increase in fog days was promoted by the abundance of aerosols (Fan et al, ; Maalick et al, ). After 1985, when urbanization accelerated, fog days decreased faster in city stations than in background stations, which was due to the combined effects of urbanization and increasing aerosols; moreover, the hindering effect of urbanization is presumed to be dominant (Sachweh & Koepke, ).…”

“…This phenomenon is also possibly due to urbanization. Therefore, fog is hypothesized to be promoted by increasing aerosols during the slow urbanization stage (Fan et al, ) and later inhibited by accelerated urbanization (Sachweh & Koepke, ).…”

Six research priorities for cities and climate change

“…For example, urban air pollution in Chinese cities is causing heavier rainfall as fine particles influence clouds 4 . Impermeable surfaces, such as concrete or asphalt, hold heat and reduce evaporative cooling, amplifying urban 'heat islands' 5 .…”

Aerosol-induced changes in the vertical structure of precipitation: a perspective of TRMM precipitation radar

“…The invigoration theory was recently generalized by Fan et al (2018) that can also occur for shallower water clouds under extreme clean conditions under which ultra-fine mode aerosol particles may be nucleated to release latent heat to fuel cloud development. While we have come a long way in understanding the mechanisms behind various observation-based findings, the impact of aerosol on precipitation remain a daunting task (Tao et al, 2012).…”