Biological particles and mineral dust are responsible for ice formation in clouds in the Amazon, according to a study published online in Nature Geoscience. Microscopic particles initiate ice formation in the atmosphere, but the identity of these particles has been a matter of debate.

Anthony Prenni and colleagues examined the chemical composition of ice-forming particles in the Amazon basin during the wet season. They show that locally produced biological particles and mineral dust account for the majority of these ice-forming particles. Using a simple model, they suggest that the contribution of local bio-particles to ice formation is increased at higher atmospheric temperatures.