Articles | Volume 17, issue 21
Atmos. Chem. Phys., 17, 12911–12940, 2017
Atmos. Chem. Phys., 17, 12911–12940, 2017
Research article
03 Nov 2017
Research article | 03 Nov 2017

Investigation of global particulate nitrate from the AeroCom phase III experiment

Huisheng Bian1,2, Mian Chin2, Didier A. Hauglustaine3, Michael Schulz4, Gunnar Myhre5, Susanne E. Bauer6,7, Marianne T. Lund5, Vlassis A. Karydis8, Tom L. Kucsera9, Xiaohua Pan10, Andrea Pozzer8, Ragnhild B. Skeie5, Stephen D. Steenrod9, Kengo Sudo11,12, Kostas Tsigaridis6,7, Alexandra P. Tsimpidi8, and Svetlana G. Tsyro4 Huisheng Bian et al.
  • 1Joint Center for Environmental Technology UMBC, Baltimore, MD, USA
  • 2Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 3Laboratoire des Sciences du Climat et de l'Environnement (LSCE), UMR8212, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
  • 4Research and Development Department, Norwegian Meteorological Institute, Oslo, Norway
  • 5Center for International Climate and Environmental Research – Oslo (CICERO), Oslo, Norway
  • 6NASA Goddard Institute for Space Studies, New York, NY, 10025, USA
  • 7Center for Climate System Research, Columbia University, New York, NY, 10025, USA
  • 8Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz, Germany
  • 9Universities Space Research Association, GESTAR, Columbia, MD, USA
  • 10School of Computer, Mathematical and Natural Sciences, Morgan State University, Baltimore, MD, USA
  • 11Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan
  • 12Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan

Abstract. An assessment of global particulate nitrate and ammonium aerosol based on simulations from nine models participating in the Aerosol Comparisons between Observations and Models (AeroCom) phase III study is presented. A budget analysis was conducted to understand the typical magnitude, distribution, and diversity of the aerosols and their precursors among the models. To gain confidence regarding model performance, the model results were evaluated with various observations globally, including ground station measurements over North America, Europe, and east Asia for tracer concentrations and dry and wet depositions, as well as with aircraft measurements in the Northern Hemisphere mid-to-high latitudes for tracer vertical distributions. Given the unique chemical and physical features of the nitrate occurrence, we further investigated the similarity and differentiation among the models by examining (1) the pH-dependent NH3 wet deposition; (2) the nitrate formation via heterogeneous chemistry on the surface of dust and sea salt particles or thermodynamic equilibrium calculation including dust and sea salt ions; and (3) the nitrate coarse-mode fraction (i.e., coarse/total). It is found that HNO3, which is simulated explicitly based on full O3-HOx-NOx-aerosol chemistry by all models, differs by up to a factor of 9 among the models in its global tropospheric burden. This partially contributes to a large difference in NO3, whose atmospheric burden differs by up to a factor of 13. The atmospheric burdens of NH3 and NH4+ differ by 17 and 4, respectively. Analyses at the process level show that the large diversity in atmospheric burdens of NO3, NH3, and NH4+ is also related to deposition processes. Wet deposition seems to be the dominant process in determining the diversity in NH3 and NH4+ lifetimes. It is critical to correctly account for contributions of heterogeneous chemical production of nitrate on dust and sea salt, because this process overwhelmingly controls atmospheric nitrate production (typically > 80 %) and determines the coarse- and fine-mode distribution of nitrate aerosol.

Short summary
Atmospheric nitrate contributes notably to total aerosol mass in the present day and is likely to be more important over the next century, with a projected decline in SO2 and NOx emissions and increase in NH3 emissions. This paper investigates atmospheric nitrate using multiple global models and measurements. The study is part of the AeroCom phase III activity. The study is the first attempt to look at global atmospheric nitrate simulation at physical and chemical process levels.
Final-revised paper