Atmospheric aerosol particles are essential for forming clouds and precipitation, thereby influencing Earth’s energy budget, water cycle and climate on regional and global scales. However, the origin of aerosol particles over the Amazon rainforest during the wet season is poorly understood. Earlier studies showed new particle formation in the outflow of deep convective clouds and suggested a downward flux of aerosol particles during precipitation events. Here we use comprehensive aerosol, trace gas and meteorological data from the Amazon Tall Tower Observatory to show that rainfall regularly induces bursts of nanoparticles in the nucleation size range. This can be attributed to rain-related scavenging of larger particles and a corresponding reduction of the condensation sink, along with an ozone injection into the forest canopy, which could increase the oxidation of biogenic volatile organic compounds, especially terpenes, and enhance new particle formation. During and after rainfall, the nucleation particle concentrations directly above the canopy are greater than those higher up. This gradient persists throughout the wet season for the nucleation size range, indicating continuous particle formation within the canopy, a net upward flux of newly formed particles and a paradigm shift in understanding aerosol–cloud–precipitation interactions in the Amazon. Particle bursts provide a plausible explanation for the formation of cloud condensation nuclei, leading to the local formation of green-ocean clouds and precipitation. Our findings suggest that an interplay of a rain-related reduction in the condensation sink, primary emissions of gases, mainly terpenes, and particles from the forest canopy, and convective cloud processing determines the population of cloud condensation nuclei in pristine rainforest air.

大气气溶胶颗粒对于形成云和降水至关重要，从而在区域和全球范围内影响地球的能源收支、水循环和气候。然而，人们对雨季亚马逊雨林上气溶胶颗粒的来源知之甚少。早期的研究表明，在深对流云的流出中会形成新的颗粒，并表明在降水事件期间气溶胶颗粒的通量向动。在这里，我们使用来自 Amazon Tall Tower Observatory 的综合气溶胶、痕量气体和气象数据来表明，降雨经常会诱发成核尺寸范围内的纳米粒子爆发。这可以归因于与雨水相关的较大颗粒的清除和冷凝汇的相应减少，以及向森林树冠注入臭氧，这可能会增加生物挥发性有机化合物（尤其是萜烯）的氧化，并促进新颗粒的形成。在降雨期间和降雨后，冠层正上方的成核颗粒浓度大于较高层的成核颗粒浓度。这种梯度在整个雨季持续存在，范围为成核大小范围，表明在冠层内形成连续的颗粒，新形成的颗粒的净向上通量以及理解亚马逊气溶胶-云-降水相互作用的范式转变。粒子爆发为云凝结核的形成提供了一个合理的解释，导致局部形成绿海云和降水。 我们的研究结果表明，与雨水相关的冷凝汇减少、气体（主要是萜烯和森林冠层颗粒）的初级排放以及对流云处理的相互作用决定了原始雨林空气中云凝结核的数量。