Ammonia plays a key role in the neutralization of atmospheric acids such as sulfate and nitrates. A few in situ observations have supported the theory that gas-phase NH₃ concentrations should decrease sharply with altitude and be extremely low in the upper troposphere and lower stratosphere (UTLS). This theory, however, seems inconsistent with recent satellite measurements and is also not supported by the aircraft data showing highly or fully neutralized sulfate aerosol particles by ammonium in the UTLS in many parts of the world. Here we reveal the contributions of deep convective clouds to NH₃ in the UTLS by using integrated cross-scale modeling, which includes molecular dynamic simulations, a global chemistry transport model, and satellite and aircraft measurements. We show that the NH₃ dissolved in liquid cloud droplets is prone to being released into the UTLS upon freezing during deep convection. Because NH₃ emission is not regulated in most countries and its future increase is likely persistent from agricultural growth and the warmer climate, the effect of NH₃ on composition and phase of aerosol particles in the UTLS can be significant, which in turn can affect cirrus cloud formation, radiation, and the budgets of NOx and O₃.

氨在中和大气酸（例如硫酸盐和硝酸盐）中起关键作用。一些原位观测结果支持了这样的理论，即气相NH ₃浓度应随海拔高度急剧下降，而在对流层和平流层下部（UTLS）则应极低。但是，该理论似乎与最近的卫星测量结果不一致，并且飞机数据也未得到支持，该数据显示在世界许多地方，UTLS中的铵盐高度或完全中和了硫酸盐气溶胶颗粒。在这里，我们揭示了深对流云对NH ₃的贡献在UTLS中使用集成的跨尺度建模，包括分子动力学模拟，全球化学传输模型以及卫星和飞机测量。我们显示，溶解在液态云滴中的NH ₃在深度对流冻结时很容易释放到UTLS中。由于大多数国家/地区都未对NH ₃排放进行监管，并且未来的增长可能会因农业增长和气候变暖而持续存在，因此NH ₃对UTLS中气溶胶颗粒组成和相的影响可能很大，进而会影响卷云云的形成，辐射以及NOx和O ₃的预算。