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Volume 18, issue 9
Atmos. Chem. Phys., 18, 6847-6866, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Global and regional assessment of intercontinental transport...

Atmos. Chem. Phys., 18, 6847-6866, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 May 2018

Research article | 16 May 2018

Multi-model study of HTAP II on sulfur and nitrogen deposition

Jiani Tan1, Joshua S. Fu1, Frank Dentener2, Jian Sun1, Louisa Emmons3, Simone Tilmes3, Kengo Sudo4, Johannes Flemming5, Jan Eiof Jonson6, Sylvie Gravel7, Huisheng Bian8, Yanko Davila9, Daven K. Henze9, Marianne T. Lund10, Tom Kucsera11, Toshihiko Takemura12, and Terry Keating13 Jiani Tan et al.
  • 1Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA
  • 2European Commission, Institute for Environment and Sustainability Joint Research Centre, Ispra, Italy
  • 3Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
  • 4Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
  • 5European Centre for Medium-Range Weather Forecasts, Reading, UK
  • 6Norwegian Meteorological Institute, Oslo, Norway
  • 7Meteorological Research Branch, Meteorological Service of Canada, Toronto, Canada
  • 8National Aeronautics and Space Administration Goddard Space Flight Center, Greenbelt, MD, USA
  • 9Department of Mechanical Engineering, University of Colorado, Boulder, CO, USA
  • 10CICERO Center for International Climate Research, Oslo, Norway
  • 11Universities Space Research Association, NASA/GESTAR, Columbia, MD, USA
  • 12Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
  • 13US Environmental Protection Agency, Washington, DC, USA

Abstract. This study uses multi-model ensemble results of 11 models from the second phase of Task Force Hemispheric Transport of Air Pollution (HTAP II) to calculate the global sulfur (S) and nitrogen (N) deposition in 2010. Modeled wet deposition is evaluated with observation networks in North America, Europe and East Asia. The modeled results agree well with observations, with 76–83% of stations being predicted within ±50% of observations. The models underestimate SO42−, NO3 and NH4+ wet depositions in some European and East Asian stations but overestimate NO3 wet deposition in the eastern United States. Intercomparison with previous projects (PhotoComp, ACCMIP and HTAP I) shows that HTPA II has considerably improved the estimation of deposition at European and East Asian stations. Modeled dry deposition is generally higher than the inferential data calculated by observed concentration and modeled velocity in North America, but the inferential data have high uncertainty, too. The global S deposition is 84Tg(S) in 2010, with 49% in continental regions and 51% in the ocean (19% of which coastal). The global N deposition consists of 59Tg(N) oxidized nitrogen (NOy) deposition and 64Tg(N) reduced nitrogen (NHx) deposition in 2010. About 65% of N is deposited in continental regions, and 35% in the ocean (15% of which coastal). The estimated outflow of pollution from land to ocean is about 4Tg(S) for S deposition and 18Tg(N) for N deposition. Comparing our results to the results in 2001 from HTAP I, we find that the global distributions of S and N deposition have changed considerably during the last 10 years. The global S deposition decreases 2Tg(S) (3%) from 2001 to 2010, with significant decreases in Europe (5Tg(S) and 55%), North America (3Tg(S) and 29%) and Russia (2Tg(S) and 26%), and increases in South Asia (2Tg(S) and 42%) and the Middle East (1Tg(S) and 44%). The global N deposition increases by 7Tg(N) (6%), mainly contributed by South Asia (5Tg(N) and 39%), East Asia (4Tg(N) and 21%) and Southeast Asia (2Tg(N) and 21%). The NHx deposition increases with no control policy on NH3 emission in North America. On the other hand, NOy deposition has started to dominate in East Asia (especially China) due to boosted NOx emission.

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We study the distributions of sulfur and nitrogen deposition, which are associated with current environmental issues such as formation of acid rain and ecosystem eutrophication and result in widespread problems such as loss of environmental diversity, harming the crop yield and even food insecurity. According to our study, both the amount and distribution of sulfate and nitrogen deposition have changed significantly in the last decade, particularly in East Asia, South Asia and Southeast Asia.
We study the distributions of sulfur and nitrogen deposition, which are associated with current...