Substantial convection and precipitation enhancements by ultrafine aerosol particles

• Published in: Science (American Association for the Advancement of Science) Vol. 359; no. 6374
• Main Authors: Fan, Jiwen, Rosenfeld, Daniel, Zhang, Yuwei, Giangrande, Scott E., Li, Zhanqing, Machado, Luiz A. T., Martin, Scot T., Yang, Yan, Wang, Jian, Artaxo, Paulo, Barbosa, Henrique M. J., Braga, Ramon C., Comstock, Jennifer M., Feng, Zhe, Gao, Wenhua, Gomes, Helber B., Mei, Fan, Pöhlker, Christopher, Pöhlker, Mira L., Pöschl, Ulrich, de Souza, Rodrigo A. F.
• Format: Journal Article
• Language: English
• Published: United States AAAS 25.01.2018
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aan8461

Aerosol-cloud interaction remains the largest uncertainty in climate projections. Ultrafine aerosol particles (UAP; size <50nm) are considered too small to serve as cloud condensation nuclei conventionally. However, this study provides observational evidence to accompany insights from numerical simulations to support that deep convective clouds (DCCs) over Amazon have strong capability of nucleating UAP from an urban source and forming greater numbers of droplets, because fast drop coalescence in these DCCs reduces drop surface area available for condensation, leading to high vapor supersaturation. The additional droplets subsequently decrease supersaturation and release more condensational latent heating, a dominant contributor to convection intensification, whereas enhanced latent heat from ice-related processes plays a secondary role. Therefore, the addition of anthropogenic UAP may play a much greater role in modulating clouds than previously believed over the Amazon region and possibly in other relatively pristine regions such as maritime and forest locations.