New publication in Nature

The article “Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation” by Mingyi Wang et al. has been published in Nature as Open Access. The authors use the global model EMAC in parts of their study for simulation of particle formation with efficient vertical transport of ammonia into the upper troposphere during the Asian monsoon.

Abstract: New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.

© Author(s) 2022. This work is distributed under the Creative Commons Attribution 4.0 License.

Wang, M., Xiao, M., Bertozzi, B. et al. Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation. Nature 605, 483–489 (2022).

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