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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-447
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
05 Jul 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
Seasonal variation of fine and coarse-mode nitrates and related aerosols over East Asia: Synergetic observations and chemical transport model analysis
Itsushi Uno1, Kazuo Osada2, Keiya Yumimoto1, Zhe Wang1,3, Syuichi Itahashi4, Xiaole Pan3, Yukari Hara1, Yugo Kanaya5, Shigekazu Yamamoto6, and Thomas Duncan Fiarlie7 1Research Institute for Applied Mechanics, Kyushu University, Kasuga Park 6-1, Fukuoka 816-8580, Japan
2Nagoya University, Graduate School of Environ. Studies, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
3Institute of Atmospheric Physics, CAS, Beijing, China
4Central Research Institute of Electric Power Industry, Abiko, Chiba, 270-1194, Japan
5Japan Agency for Marine-Earth Science and Technology, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan
6Fukuoka Institute of Health and Environmental Sciences, Mukaizano 39, Dazaifu, Fukuoka 818-0135, Japan
7NASA, Langley Research Center, Hampton, VA 23681-0001, USA
Abstract. We analyzed long-term fine- and coarse-mode nitrate and related aerosols (SO42−, NO3, NH4+, Na+, Ca2+) synergetic observations at Fukuoka (33.52° N, 130.47° E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea-salt acid uptake processes was used to assess the observed seasonal variation, and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO42−, fNO3, and fNH4+), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85 % for fSO42−, 47 % for fNO3, 73 % for fNH4+). Observational data for HNO3, fNO3, and coarse NO3 (cNO3) confirmed that cNO3 made up the largest proportion of total nitrate (defined as the sum of fNO3, cNO3 and HNO3), constituting 40–55 % of total nitrate during the winter, while HNO3 gas constituted approximately 40 % of total nitrate in summer, and fNO3 peaked during the winter. A numerical model reproduced the seasonal variations in fNO3. For cNO3, large-scale dust-nitrate outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. Modeled cNO3 was in good agreement with observations between July and November (mainly coming from sea salt-NO3). However during the winter, the model underestimated cNO3 levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA). We used cNa+, nss-cCa2+, and cNH4+ as independent variables to describe the observed cNO3 levels; these variables were considered representative of sea salt-cNO3, dust-cNO3, and cNO3 accompanied by cNH4+ (cNH4+ term), respectively. The MRA results explained the observed seasonal changes in dust-cNO3 and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43 % (sea salt-cNO3), 19 % (dust cNO3), and 38 % (cNH4+ term). The MRA dust-cNO3 component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNH4+ term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3 and SO42− and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO3 formation, especially in winter.

Citation: Uno, I., Osada, K., Yumimoto, K., Wang, Z., Itahashi, S., Pan, X., Hara, Y., Kanaya, Y., Yamamoto, S., and Fiarlie, T. D.: Seasonal variation of fine and coarse-mode nitrates and related aerosols over East Asia: Synergetic observations and chemical transport model analysis, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-447, in review, 2017.
Itsushi Uno et al.
Itsushi Uno et al.

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We analyzed long-term fine- and coarse-mode nitrate and related aerosols synergetic observations at Fukuoka, Japan. GEOS Chem model including dust and sea-salt acid uptake processes was used to assess the observed seasonal variation, and the impact of long-range transport from the Asian continent. A numerical model reproduced the seasonal variations of fine aerosols. For coarse nitrate, large-scale dust-nitrate outflow from China was confirmed during all dust events between January and June.
We analyzed long-term fine- and coarse-mode nitrate and related aerosols synergetic observations...
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