Small Particles Play Large Role in Tropical Thunderstorms

Fan, J., Pacific Northwest National Laboratory

Aerosol Properties

Aerosol Processes

Fan J, D Rosenfeld, Y Zhang, S Giangrande, Z Li, L Machado, S Martin, Y Yang, J Wang, P Artaxo, H Barbosa, R Braga, J Comstock, Z Feng, W Gao, H Gomes, F Mei, C Pöhlker, M Pöhlker, U Pöschl, and R de Souza. 2018. "Substantial convection and precipitation enhancements by ultrafine aerosol particles." Science, 359(6374), 10.1126/science.aan8461.

Science

Aerosol-cloud interactions remain the largest uncertainty in climate projections. Ultrafine aerosol particles—less than 50 nanometers wide—can be abundant in the troposphere, but are conventionally considered too small to affect cloud formation. A unique set of observations from the Amazon allowed scientists, to study the role of aerosols in tropical storm cloud development. Through observational evidence and numerical simulations, they found that when tiny particles outnumber larger particles in a warm and humid environment, the result is enhanced condensation that releases more heat, producing much more powerful updrafts. More warm air is pulled into the clouds, lifting more droplets aloft and producing more ice and snow pellets, lightning, and rain.

Impact

Through the newly discovered enhanced condensation mechanism, ultrafine aerosols, whose effects on clouds have been largely neglected until now, are found to invigorate thunderstorms in a much more powerful way than their larger counterparts. The finding suggests that from pre-industrial times to the present day, human activity such as urbanization and industry may have significantly influenced storms in warm and humid places, such as tropical and some subtropical regions.

Summary

Through the newly discovered enhanced condensation mechanism, ultrafine aerosols, the effects of which on clouds have been largely neglected until now, are found to invigorate thunderstorms in a much more powerful way than their larger counterparts. The finding suggests that from pre-industrial times to the present day, human activity such as urbanization and industry may have significantly influenced storms in warm and humid places, such as tropical and some subtropical regions.