Quantitative simulation of an aerosol’s lifecycle by regional-scale and global-scale atmospheric models is mandatory for unbiased analysis and prediction of aerosol radiative forcing and climate change. Globally, aerosol deposition is dominated by the rainout process, which is mostly triggered by activation of aerosols to liquid droplets in supersaturated domains of precipitating clouds. However, the actual environmental supersaturation value that aerosols experience in precipitating clouds is difficult for models to predict, and it has never been constrained by observations; as a result, there is large uncertainty in atmospheric aerosol simulations. Here, by a particle-tracer analysis of 37 rainfall events in East Asia, near the largest source region of anthropogenic aerosols in the northern hemisphere, we observed that the environmental supersaturation actually experienced by the removed aerosols in precipitating clouds averaged 0.08 ± 0.03% and ranged from 0.03 to 0.2%. Simulations by a mixing-state-resolved global aerosol model showed that the simulated long-range transport efficiency and global atmospheric burden of black carbon aerosols can be changed by a factor of two or three as a result of a change in the environmental supersaturation in precipitating clouds within just 0.08 ± 0.03%. This result is attributable to the fact that the sensitivity of an aerosol’s rainout efficiency to environmental supersaturation is higher for the less-aged black carbon concentrated near source regions. Our results suggest that observational constraints of environmental supersaturation in precipitating clouds, particularly near source regions, are of fundamental importance for accurate simulation of the atmospheric burden of black carbon and other aerosols.

通过区域尺度和全球尺度的大气模型对气溶胶生命周期进行定量模拟，对于气溶胶辐射强迫和气候变化的无偏分析和预测是必不可少的。在全球范围内，气溶胶沉积主要由降雨过程决定，降雨过程主要是由气溶胶活化成沉淀云的过饱和域中的液滴引起的。但是，气溶胶在云层中所经历的实际环境过饱和度值很难用模型来预测，而且从未受到观测值的限制。结果，大气气溶胶模拟存在很大的不确定性。在这里，通过对近东北半球最大的人为气溶胶来源地区附近的东亚37个降雨事件的颗粒示踪分析，我们观察到，去除的气溶胶在降水云中实际经历的环境过饱和度平均为0.08±0.03％，范围为0.03至0.2％。通过混合状态解析的全球气溶胶模型进行的模拟表明，由于沉淀过程中环境过饱和度的变化，模拟的黑碳气溶胶的远距离传输效率和全球大气负荷可以改变两个或三个因子。仅在0.08±0.03％的范围内。该结果归因于以下事实：对于集中在源区附近的年龄较小的黑碳，气溶胶的降雨效率对环境过饱和的敏感性更高。我们的结果表明，在降水云中，尤其是在源区附近，环境过饱和的观测约束，