Model Inter-Comparison Study for Asia (MICS-Asia) phase III: multimodel comparison of reactive nitrogen deposition over China
Authors: Ge Baozhu , Itahashi Syuichi , Sato Keiichi , Xu Danhui , Wang Junhua , Fan Fan , Tan Qixin , Fu Joshua S. , Wang Xuemei , Yamaji Kazuyo , Nagashima Tatsuya , Li Jie , Kajino Mizuo , Liao Hong , Zhang Meigen , Wang Zhe , Li Meng , Woo Jung-Hun , Kurokawa Junichi , Pan Yuepeng , Wu Qizhong , Liu Xuejun , Wang Zifa 
Published: September 2020

Abstract. Atmospheric nitrogen deposition in China has attracted public attention in recent years due to the
increasing anthropogenic emission of reactive nitrogen (Nr) and its impacts on the
terrestrial and aquatic ecosystems. However, limited long-term and multisite measurements have
restrained the understanding of the mechanism of the Nr deposition and the
chemical transport model (CTM) improvement. In this study, the performance of the simulated wet
and dry deposition for different Nr species, i.e., particulate NO3- and
NH4+, gaseous NOx, HNO3 and NH3 have been
conducted using the framework of Model Inter-Comparison Study for Asia (MICS-Asia) phase III. A total of nine
models, including five Weather Research and Forecasting models coupled with the Community Multiscale
Air Quality (WRF-CMAQ) models, two self-developed regional models, a global model and a Regional Atmospheric Modeling System coupled with the Community Multiscale
Air Quality (RAMS-CMAQ) model have been selected for the comparison. For wet deposition, observation data from 83 measurement sites from the East Asia Acid Deposition Monitoring Network (EANET), Chinese Ecosystem Research Network (CERN), China Agricultural University Deposition Network (CAUDN), National Acid Deposition Monitoring Network (NADMN) and Department of
Ecological Environment (DEE) of China have been collected and
normalized for comparison with model results. In general, most models show the consistent spatial and
temporal variation of both oxidized N (Nox) and reduced N (Nrd) wet
deposition in China, with the normalized mean error (NME) at around 50 %, which is lower than the value of 70 %
based on EANET observation over Asia. Both the ratio of wet or dry deposition to the total
inorganic N (TIN) deposition and the ratios of TIN to their emissions have shown consistent
results with the Nationwide Nitrogen Deposition
Monitoring Network (NNDMN) estimates. The performance of ensemble results (ENMs) was further assessed
with satellite measurements. In different regions of China, the results show that the simulated
Nox wet deposition was overestimated in northeastern China (NE) but underestimated in the
south of China, namely southeastern (SE) and southwestern (SW) China, while the Nrd wet deposition was underestimated in all
regions by all models. The deposition of Nox has larger uncertainties than the
Nrd, especially in northern China (NC), indicating the chemical reaction process is one of
the most important factors affecting the model performance. Compared to the critical load (CL) value,
the Nr deposition in NC, SE and SW reached or exceeded reported CL values and resulted
in serious ecological impacts. The control of Nrd in NC and SW and Nox in SE
would be an effective mitigation measure for TIN deposition in these regions. The Nr deposition in
the Tibetan Plateau (TP) with a high ratio of TIN ∕ emission (∼3.0), indicates a significant
transmission from outside. Efforts to reduce these transmissions ought to be paramount due
the climatic importance of the Tibetan region to the sensitive ecosystems throughout China.