# Model Inter-Comparison Study for Asia (MICS-Asia) phase III: multimodel comparison of reactive nitrogen deposition over China

Atmospheric nitrogen deposition in China has attracted public attention in recent years due to the increasing anthropogenic emission of reactive nitrogen (inline-formulaNr) 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 inline-formulaNr deposition and the chemical transport model (CTM) improvement. In this study, the performance of the simulated wet and dry deposition for different inline-formulaNr species, i.e., particulate inline-formula $M4inlinescrollmathmlchem{\mathrm{normal NO}}_{normal 3}^{-}$ 25pt16ptsvg-formulamathimge16cba38499a6a16cb1a10e488ec56da acp-20-10587-2020-ie00001.svg25pt16ptacp-20-10587-2020-ie00001.png and inline-formula $M5inlinescrollmathmlchem{\mathrm{normal NH}}_{normal 4}^{+}$ 24pt15ptsvg-formulamathimg68d940fa21d9c6691de36bd82f3e56d8 acp-20-10587-2020-ie00002.svg24pt15ptacp-20-10587-2020-ie00002.png , gaseous inline-formulaNOx, inline-formulaHNO3 and inline-formulaNH3 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 (inline-formulaNox) and reduced N (inline-formulaNrd) 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 inline-formulaNox wet deposition was overestimated in northeastern China (NE) but underestimated in the south of China, namely southeastern (SE) and southwestern (SW) China, while the inline-formulaNrd wet deposition was underestimated in all regions by all models. The deposition of inline-formulaNox has larger uncertainties than the inline-formulaNrd, 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 inline-formulaNr deposition in NC, SE and SW reached or exceeded reported CL values and resulted in serious ecological impacts. The control of inline-formulaNrd in NC and SW and inline-formulaNox in SE would be an effective mitigation measure for TIN deposition in these regions. The inline-formulaNr deposition in the Tibetan Plateau (TP) with a high ratio of TIN inline-formula∕ emission (inline-formula∼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.

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Ge, Baozhu / Itahashi, Syuichi / Sato, Keiichi / et al: Model Inter-Comparison Study for Asia (MICS-Asia) phase III: multimodel comparison of reactive nitrogen deposition over China. 2020. Copernicus Publications.

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