Biomass Burning Smoke and Its Influence on Clouds Over the Western U. S.
C. H. Twohy, D. W. Toohey, Ezra J. T. Levin, Paul J. DeMott, Bryan Rainwater, Lauren A. Garofalo, Matson A. Pothier, Delphine K. Farmer, Sonia M. Kreidenweis, Rudra P. Pokhrel, S. M. Murphy, J. M. Reeves, Kathryn A. Moore, Emily V. Fischer
Abstract
Abstract Small cumulus clouds over the western United States were measured via airborne instruments during the wildfire season in summer of 2018. Statistics of the sampled clouds are presented and compared to smoke aerosol properties. Cloud droplet concentrations were enhanced in regions impacted by biomass burning smoke, at times exceeding 3,000 cm −3 . Images and elemental composition of individual smoke particles and cloud droplet residuals are presented and show that most are dominantly organic, internally mixed with some inorganic elements. Despite their high organic content and relatively low hygroscopicity, on average about half of smoke aerosol particles >80 nm diameter formed cloud droplets. This reduced cloud droplet size in small, smoke‐impacted clouds. A number of complex and competing climatic impacts may result from wide‐spread reductions in cloud droplet size due to wildfires prevalent across the region during summer months.