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.

中文翻译：

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生物质燃烧烟雾及其对美国西部云层的影响

在 2018 年夏季的野火季节期间，通过机载仪器测量了美国西部上空的小积云。提供了采样云的统计数据，并与烟雾气溶胶特性进行了比较。在受生物质燃烧烟雾影响的地区，云滴浓度增加，有时超过 3,000 cm ^-3. 呈现了单个烟雾颗粒和云滴残留物的图像和元素组成，表明大多数主要是有机的，内部与一些无机元素混合。尽管它们的有机物含量高且吸湿性相对较低，但平均约一半的烟雾气溶胶颗粒> 80 nm 直径形成了云滴。这减小了受烟雾影响的小云中的云滴大小。由于夏季月份该地区普遍存在野火，云滴大小的广泛减少可能会导致许多复杂且相互竞争的气候影响。