Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation
Mingyi Wang, Mao Xiao, Barbara Bertozzi, Guillaume Marie, Birte Rörup, Benjamin C. Schulze, Roman Bardakov, Xu‐Cheng He, Jiali Shen, Wiebke Scholz, Ruby Marten, Lubna Dada, Rima Baalbaki, Brandon Lopez, Houssni Lamkaddam, Hanna E. Manninen, A. Amorim, Farnoush Ataei, Pia Bogert, Zoé Brasseur, Lucía Caudillo, Louis-Philippe De Menezes, Jonathan Duplissy, Annica M. L. Ekman, Henning Finkenzeller, Loïc Gonzalez Carracedo, Manuel Granzin, R. Guida, Martin Heinritzi, Victoria Hofbauer, Kristina Höhler, Kimmo Korhonen, Jordan Krechmer, Andreas Kürten, Katrianne Lehtipalo, Naser Mahfouz, В. С. Махмутов, Dario Massabò, Serge Mathot, Roy L. Mauldin, Bernhard Mentler, Tatjana Müller, Antti Onnela, Tuukka Petäjä, Maxim Philippov, Ana A. Piedehierro, Andrea Pozzer, Ananth Ranjithkumar, Meredith Schervish, Siegfried Schobesberger, Mario Simon, Yuri Stozhkov, António Tomé, Nsikanabasi Silas Umo, Franziska Vogel, Robert Wagner, Dongyu Wang, Stefan K. Weber, André Welti, Yusheng Wu, Marcel Zauner-Wieczorek, Mikko Sipilä, Paul M. Winkler, Armin Hansel, Urs Baltensperger, Markku Kulmala, Richard C. Flagan, Joachim Curtius, Ilona Riipinen, Hamish Gordon, Jos Lelieveld, Imad El Haddad, Rainer Volkamer, Douglas R. Worsnop, T. Christoudias, J. Kirkby, Ottmar Möhler, Neil M. Donahue
Abstract
Abstract New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN) 1–4 . 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 5,6 . 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 HNO 3 –H 2 SO 4 –NH 3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.