This award supported measurements of condensed water, residual particles that remain after evaporating droplets in clouds, and aerosols in air affefcted by smoke from large wildfires in the Western United States. Observations used the National Center for Atmospheric Research (NCAR) Counterflow Virtual Impactor (CVI) on the NSF C-130 reserach aircraft. Multiple instruments measured air sampled by the inlet in real time and one instrument collected particulate matter for subsequent analysis in specialized laboratory equipment. Another instrument measured the ability for some smoke particles to cause cloud droplets to freeze ("ice nucleation"). This work was motivated by a need to improve understanding of the ways in which clouds and precipitation are affected by wildfire smoke, in particular how particulate matter that is dark (e.g., "black carbon" and "brown carbon") is taken up into clouds and removed from the atmosphere. The observations addressed gaps in knowledge of the chemical composition of nuclei that are taken up by clouds and the mechanisms for altering cloud litetimes and reflection of sunlight (i.e., "albedo").  It was found that particles composed of black and brown carbon are taken up more readily than was expected prior to the observations, and that cloud lifetimes were significantly altered by that uptake. It is likely that other compounds emitted by the wildfire, including sulfur compounts and carbon compounds that react to form acids in the atmosphere, are responsible for altering the surfaces of black and brown carbon, thus making them more soluble in clouds.These results will lead to improved model forecasts of cloud formation and precipitation influenced by smoke from large wildfires, and improve understanding of the role of clouds in Earth’s weather and climate. The results have been published in multiple articles in the peer-reviewed scientific literature.

Last Modified: 07/11/2023
Modified by: Darin W Toohey